This makes it easier to spot syntax errors when editing the
class reference. The schema is referenced locally so validation
can still work offline.
Each class XML's schema conformance is also checked on GitHub Actions.
* Functions to convert to/from degrees are all gone. Conversion is done by the editor.
* Use PROPERTY_HINT_ANGLE instead of PROPERTY_HINT_RANGE to edit radian angles in degrees.
* Added possibility to add suffixes to range properties, use "min,max[,step][,suffix:<something>]" example "0,100,1,suffix:m"
* In general, can add suffixes for EditorSpinSlider
Not covered by this PR, will have to be addressed by future ones:
* Ability to switch radians/degrees in the inspector for angle properties (if actually wanted).
* Animations previously made will most likely break, need to add a way to make old ones compatible.
* Only added a "px" suffix to 2D position and a "m" one to 3D position, someone needs to go through the rest of the engine and add all remaining suffixes.
* Likely also need to track down usage of EditorSpinSlider outside properties to add suffixes to it too.
We already removed it from the online docs with #35132.
Currently it can only be "Built-In Types" (Variant types) or "Core"
(everything else), which is of limited use.
We might also want to consider dropping it from `ClassDB` altogether
in Godot 4.0.
