Replace text instead of whole header when numbering/clearing

[sheikgit]

Slightly modify the code to replace header numbering text substrings when both clearing and numbering instead of replacing the whole header. This prevents comments of the numbered header to be erased.

[jordan2175]

I noticed with this change, the formatting for the heading number does not match the style. It is like the "heading style" is not being applied to the number as it is added.

[lpanebr]

Sorry for taking so long. I did a lot of fixes today, including that, and just now remembered about the PRs. Please fell free to contribute again and I'll be more active. Thanks!!!