Style: Misc docs and comment style and language fixes

- Removed empty paragraphs in XML.
- Consistently use bold style for "Example:", on a new line.
- Fix usage of `[code]` when hyperlinks could be used (`[member]`, `[constant]`).
- Fix invalid usage of backticks for inline code in BBCode.
- Fix some American/British English spelling inconsistencies.
- Other minor fixes spotted along the way, including typo fixes with codespell.
- Don't specify `@GlobalScope` for `enum` and `constant`.

doc/classes/VisualShaderNodeInput.xml

@@ -19,7 +19,7 @@
 	</methods>
 	<members>
 		<member name="input_name" type="String" setter="set_input_name" getter="get_input_name" default="&quot;[None]&quot;">
-			One of the several input constants in lower-case style like: "vertex"([code]VERTEX[/code]) or "point_size"([code]POINT_SIZE[/code]).
+			One of the several input constants in lower-case style like: "vertex" ([code]VERTEX[/code]) or "point_size" ([code]POINT_SIZE[/code]).
 		</member>
 	</members>
 	<signals>