Update Content-Type header for RSS feed

Using the XSL stylesheet requires using application/xml instead of
Add XSL stylesheet for feed index
Update RSS feed

Use best practices from [1]. Specifically:

1. Add caching information in Cache-Control header and <ttl> field
2. Make the lastBuildDate equal to when the RSS feed itself was built
   last, not the date of the most recent entry
3. Only include blog posts in feed
4. Include entire post content in feed rather than just the summary
5. Set Content-Type to application/rss+xml

[1]: https://kevincox.ca/2022/05/06/rss-feed-best-practices/
Remove draft status from Neovim 0.7 post
Create draft for Neovim 0.7 post
Another fixup for pairs values
Fix my bad hex math
Update tmux article
Update hugo version for netlify
Fix sourcehut link
Split Mach-O post into 4 parts
Remove CpuSubType enum
Start on Mach-O post
Remove well-known matrix files
Fix broken links in project listing
Update project listing
Update about page
Update PGP public key