Improved Markdown generation in make_md.py: (Redot-Engine#1200)

* Improved Markdown generation in `make_md.py`:

- Updated anchor creation for consistency.
- Added `_category_.json` generation for better doc indexing.
- Introduced escaping functionality for special characters in descriptions and MD files.
- Enhanced sanitization logic for class/file/operator names.
- Streamlined Markdown reference links and tag escaping logic.

Author: Arctis-Fireblight

doc/classes/Engine.xml

@@ -48,7 +48,7 @@
 			<return type="Dictionary" />
 			<description>
 				Returns a [Dictionary] of categorized donor names. Each entry is an [Array] of strings:
-				{[code]donors[/code]}
+				[code]donors[/code]
 			</description>
 		</method>
 		<method name="get_frames_drawn">