Proofread and improve the whole class reference

- Document a few more properties and methods
- Add more information to many classes
- Fix lots of typos and gramar mistakes
- Use [code] tags for parameters consistently
- Use [b] and [i] tags consistently
- Put "Warning:" and "Note:" on their own line to be more visible,
  and make them always bold
- Tweak formatting in code examples to be more readable
- Use double quotes consistently
- Add more links to third-party technologies

doc/classes/ConvexPolygonShape2D.xml

@@ -1,10 +1,10 @@
 <?xml version="1.0" encoding="UTF-8" ?>
 <class name="ConvexPolygonShape2D" inherits="Shape2D" category="Core" version="3.2">
 	<brief_description>
-		Convex Polygon Shape for 2D physics.
+		Convex polygon shape for 2D physics.
 	</brief_description>
 	<description>
-		Convex Polygon Shape for 2D physics. A convex polygon, whatever its shape, is internally decomposed into as many convex polygons as needed to ensure all collision checks against it are always done on convex polygons (which are faster to check).
+		Convex polygon shape for 2D physics. A convex polygon, whatever its shape, is internally decomposed into as many convex polygons as needed to ensure all collision checks against it are always done on convex polygons (which are faster to check).
 		The main difference between a [ConvexPolygonShape2D] and a [ConcavePolygonShape2D] is that a concave polygon assumes it is concave and uses a more complex method of collision detection, and a convex one forces itself to be convex in order to speed up collision detection.
 	</description>
 	<tutorials>