Wiki: Update guide and add disclaimers to wiki files automatically

[balacij]

Changes:

1. Updates the Contributor's Guide with information about updating the wiki.
2. Automatically adds wiki-edit disclaimers to the top of all of our .md files (sans _Sidebar.md) in the ./wiki/ folder. Further, ensures that nobody manually adds it.
3. Removes a contributors.txt file that I accidentally committed in #3771.
4. Uses rsync instead of cp to copy over changes (this way we can sync deletions in addition to copies... we will probably need to propagate this change to #3704).

Tests:

• You can see my wiki: https://github.com/balacij/Drasil/wiki
• Latest Actions run on my repo: https://github.com/balacij/Drasil/actions/runs/9386107328/job/25845853960 -- fixed an issue regarding the grep command related to (2) that ensures nobody manually added the warnings.

[JacquesCarette]

So is this actually ready for review?

[balacij]

Yes :smile:

[balacij]

Thanks! I think it was your idea, actually, from #3771, I was just following up but forgot to write that in the OP :open_mouth:

Changes have already propagated, for anyone curious -- see the top of our wiki pages -- https://github.com/JacquesCarette/Drasil/wiki

[smiths]

Nice!