MKDocs conversion

[Shrinks99]

Closes #252, partially addresses #250

Changes

• ReplayWeb.page uses MKDocs for documentation now!
  • The rwp_version variable in mkdocs.yml must be updated every release
• Unused images have been removed
• Removes Jekyll & related site assets.

All pages have recieved copy edits. All references to future (or previously) planned features have been removed. More major content changes of note are as follows:

Supported Locations

• Moved to the develop section
• Made into a page, no longer a table. Locations are either supported or not listed!

Offline Use

• Comments out the PWA section
  • Browsers actually don't seem to cache this currently and it does not work reliably offline.
• Removes navigation instructions to GitHub's releases section in favour of a link!

Supported Formats

• Moved to the User Guide homepage
• Updated the format support!

Remove Usage, Examples, and Troubleshooting Pages

• Usage content is covered in the user guide index
• Troubleshooting content has been added to a question section on the getting started page about WARC vs WACZ.
• Examples are now Featured Projects on the docs homepage! I imagine this will be moved elsewhere to a marketing site eventually, but people have made stuff with ReplayWebpage and it would be good to show it off here!

Caveats

• I've copied the docs CI from Browsertrix but because I've removed Jekyll this will likely break things as they exist today, how will the site deploy in the future?
• The rwp_version variable uses mkdocs-macros which must be installed separately