Add new feed URL, adding /feed to category, tag, type, search, author. Eg. /category/htmly/feed

Far more easier to remember

It's easier to understand more optimal for managing static pages.

The Greek language updated by Yannis Spyrou, sent via email

Properly handle if missing title tag when write offline. The title eg. `Untitled post: Sunday, 17 December 2023, 18:53`

$_SERVER['REQUEST_URI'] is always url-encoded so we decoded it back before save it as a cache file.

Allows us to reuse previous uploaded images.
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See  #564

Add SECURITY.md also fix unexpected behavior with tags in number. See #614