Improve JSON-related documentation

This closes https://github.com/godotengine/godot-docs/issues/3848.

doc/classes/JSON.xml

@@ -15,7 +15,7 @@
 			<argument index="0" name="json" type="String">
 			</argument>
 			<description>
-				Parses a JSON encoded string and returns a [JSONParseResult] containing the result.
+				Parses a JSON-encoded string and returns a [JSONParseResult] containing the result.
 			</description>
 		</method>
 		<method name="print">
@@ -29,6 +29,7 @@
 			</argument>
 			<description>
 				Converts a [Variant] var to JSON text and returns the result. Useful for serializing data to store or send over the network.
+				[b]Note:[/b] The JSON specification does not define integer or float types, but only a [i]number[/i] type. Therefore, converting a Variant to JSON text will convert all numerical values to [float] types.
 			</description>
 		</method>
 	</methods>

doc/classes/JSONParseResult.xml

@@ -15,21 +15,21 @@
 			The error type if the JSON source was not successfully parsed. See the [enum Error] constants.
 		</member>
 		<member name="error_line" type="int" setter="set_error_line" getter="get_error_line" default="-1">
-			The line number where the error occurred if JSON source was not successfully parsed.
+			The line number where the error occurred if the JSON source was not successfully parsed.
 		</member>
 		<member name="error_string" type="String" setter="set_error_string" getter="get_error_string" default="&quot;&quot;">
-			The error message if JSON source was not successfully parsed. See the [enum Error] constants.
+			The error message if the JSON source was not successfully parsed. See the [enum Error] constants.
 		</member>
 		<member name="result" type="Variant" setter="set_result" getter="get_result">
-			A [Variant] containing the parsed JSON. Use [method @GDScript.typeof] or the [code]is[/code] keyword to check if it is what you expect. For example, if the JSON source starts with curly braces ([code]{}[/code]), a [Dictionary] will be returned. If the JSON source starts with braces ([code][][/code]), an [Array] will be returned.
+			A [Variant] containing the parsed JSON. Use [method @GDScript.typeof] or the [code]is[/code] keyword to check if it is what you expect. For example, if the JSON source starts with curly braces ([code]{}[/code]), a [Dictionary] will be returned. If the JSON source starts with brackets ([code][][/code]), an [Array] will be returned.
-			[b]Note:[/b] The JSON specification does not define integer or float types, but only a number type. Therefore, parsing a JSON text will convert all numerical values to float types.
+			[b]Note:[/b] The JSON specification does not define integer or float types, but only a [i]number[/i] type. Therefore, parsing a JSON text will convert all numerical values to [float] types.
 			[b]Note:[/b] JSON objects do not preserve key order like Godot dictionaries, thus, you should not rely on keys being in a certain order if a dictionary is constructed from JSON. In contrast, JSON arrays retain the order of their elements:
 			[codeblock]
 			var p = JSON.parse('["hello", "world", "!"]')
 			if typeof(p.result) == TYPE_ARRAY:
 			    print(p.result[0]) # Prints "hello"
 			else:
-			    print("unexpected results")
+			    push_error("Unexpected results.")
 			[/codeblock]
 		</member>
 	</members>

modules/gdscript/doc_classes/@GDScript.xml

@@ -735,16 +735,17 @@
 			<argument index="0" name="json" type="String">
 			</argument>
 			<description>
-				Parse JSON text to a Variant (use [method typeof] to check if it is what you expect).
+				Parse JSON text to a Variant. (Use [method typeof] to check if the Variant's type is what you expect.)
-				Be aware that the JSON specification does not define integer or float types, but only a number type. Therefore, parsing a JSON text will convert all numerical values to [float] types.
+				[b]Note:[/b] The JSON specification does not define integer or float types, but only a [i]number[/i] type. Therefore, parsing a JSON text will convert all numerical values to [float] types.
-				Note that JSON objects do not preserve key order like Godot dictionaries, thus you should not rely on keys being in a certain order if a dictionary is constructed from JSON. In contrast, JSON arrays retain the order of their elements:
+				[b]Note:[/b] JSON objects do not preserve key order like Godot dictionaries, thus, you should not rely on keys being in a certain order if a dictionary is constructed from JSON. In contrast, JSON arrays retain the order of their elements:
 				[codeblock]
-				p = parse_json('["a", "b", "c"]')
+				var p = JSON.parse('["hello", "world", "!"]')
-				if typeof(p) == TYPE_ARRAY:
+				if typeof(p.result) == TYPE_ARRAY:
-				    print(p[0]) # Prints a
+				    print(p.result[0]) # Prints "hello"
 				else:
-				    print("unexpected results")
+				    push_error("Unexpected results.")
 				[/codeblock]
+				See also [JSON] for an alternative way to parse JSON text.
 			</description>
 		</method>
 		<method name="polar2cartesian">
@@ -1220,12 +1221,16 @@
 			<argument index="0" name="var" type="Variant">
 			</argument>
 			<description>
-				Converts a Variant [code]var[/code] to JSON text and return the result. Useful for serializing data to store or send over the network.
+				Converts a [Variant] [code]var[/code] to JSON text and return the result. Useful for serializing data to store or send over the network.
 				[codeblock]
+				# Both numbers below are integers.
 				a = { "a": 1, "b": 2 }
 				b = to_json(a)
 				print(b) # {"a":1, "b":2}
+				# Both numbers above are floats, even if they display without any decimal places.
 				[/codeblock]
+				[b]Note:[/b] The JSON specification does not define integer or float types, but only a [i]number[/i] type. Therefore, converting a [Variant] to JSON text will convert all numerical values to [float] types.
+				See also [JSON] for an alternative way to convert a [Variant] to JSON text.
 			</description>
 		</method>
 		<method name="type_exists">
@@ -1268,9 +1273,9 @@
 				j = to_json([1, 2, 3])
 				v = validate_json(j)
 				if not v:
-				    print("valid")
+				    print("Valid JSON.")
 				else:
-				    prints("invalid", v)
+				    push_error("Invalid JSON: " + v)
 				[/codeblock]
 			</description>
 		</method>