✨ feat: enhance Table of Contents

- Introduce `toc_ignore_pattern` to ignore specific headers based on regex.
- Allow custom ToC placement with shortcode or "<!-- toc -->" marker.
- Increase max depth for ToC to 4.
- Update Documentation for the above features.
 - Move ToC generation to a macro file.

templates/shortcodes/toc.html

@@ -0,0 +1,2 @@
+{# Inserts special string to add the Table of Contents anywhere on a post #}
+<!-- toc -->