Mark '.exe', '.iso', '.dmg' as known extensions.

'EXE' is IANA registered, and the registered media type is used here for
the '.exe' extension.

The '.iso' and '.dmg' extensions do not appear to correspond to any IANA
registered media type, but they have a de facto media type of
"application/octet-stream", and that media type is used by this commit.

Closes #2530.

core/http/src/header/known_media_types.rs

@@ -52,6 +52,7 @@ macro_rules! known_media_types {
         EPUB (is_epub): "EPUB", "application", "epub+zip",
         EventStream (is_event_stream): "SSE stream", "text", "event-stream",
         Markdown (is_markdown): "markdown text", "text", "markdown" ; "charset" => "utf-8",
+        EXE (is_exe): "executable", "application", "vnd.microsoft.portable-executable",
     })
 }
 
@@ -95,6 +96,8 @@ macro_rules! known_extensions {
         "aac" => AAC,
         "ics" => Calendar,
         "bin" => Binary,
+        "iso" => Binary,
+        "dmg" => Binary,
         "mpg" => MPEG,
         "mpeg" => MPEG,
         "tar" => TAR,
@@ -109,6 +112,7 @@ macro_rules! known_extensions {
         "epub" => EPUB,
         "md" => Markdown,
         "markdown" => Markdown,
+        "exe" => EXE,
     })
 }