Add support to toggleable headings

[mariosimao]

No description provided.

[codecov-commenter]

Codecov Report

Merging #126 (d5346d7) into main (6ab4231) will increase coverage by 1.42%.
The diff coverage is 100.00%.

❗ Current head d5346d7 differs from pull request most recent head d0c84a5. Consider uploading reports for the commit d0c84a5 to get more accurate results

@@             Coverage Diff              @@
##               main     #126      +/-   ##
============================================
+ Coverage     95.58%   97.01%   +1.42%     
- Complexity      932      951      +19     
============================================
  Files           108      109       +1     
  Lines          2946     3017      +71     
============================================
+ Hits           2816     2927     +111     
+ Misses          130       90      -40     

Impacted Files	Coverage Δ
src/Blocks/Bookmark.php	94.28% <100.00%> (ø)
src/Blocks/Heading1.php	100.00% <100.00%> (+4.65%)	⬆️
src/Blocks/Heading2.php	100.00% <100.00%> (+4.65%)	⬆️
src/Blocks/Heading3.php	100.00% <100.00%> (+4.65%)	⬆️
src/Exceptions/HeadingException.php	100.00% <100.00%> (ø)
src/Blocks/BlockMetadata.php	100.00% <0.00%> (+14.28%)	⬆️
src/Exceptions/BlockException.php	100.00% <0.00%> (+33.33%)	⬆️
... and 2 more

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