Add lightbox on images
Add link to repo in footer
Use summary as page title if present
Refactor, archive page, attachments fixes

- move functions to `lib.php`
- add options to update and delete cache entry
- add archive page (list entries in cache)
- support video
- add 'noopener noreferrer' to links
- fix opengraph render
Move css out of template
og: support no og-fied pages, add fallback icon

if a page doesn't have opengraph meta tags, extract title and build
'minimal' data to be shown.
if og's article has no image, show a fallback icon.
opengraph: better style for 'article' type
Show first link og data if no attachments in post
Fix warnings printing error
improve title

decode html entities before splitting string.
Display only images attachments, fix css
Use `preferredUsername` if `name` is not set

for author display
url input keep values between posts
`http_get()` opt `$acceipt`, throw `HttpException`
Ease debugging
Tweak images css
Remove debug code
Better post title?
Better html title
Image attachments