Port 08f49bdb0d to the glitch flavour

Port 9110db41c5 to glitch

Port of 38b9af76a2 to glitch

Port 5131012505 to glitch

Ports 219aac7800 to glitch-soc

Port 379cdfaac5 to glitch-soc flavour

Port 41a01bec23 to glitch-soc

Ports cfa9b6e13a to glitchsoc

Since 245816ab2721f386184878d71be01143d207abf5, IntersectionObserverArticle
assumes that its children do not change unless the number of children changes.

This is not the case with the notification overlay, which resulted in the
checkmark of notification cleaning mode not updating unless scrolling to make
notifications appear/disappear.

This change may negatively impact performances.

This backports 0b888acfd4

This is a backport of b6af88192f to the glitch flavour.

This makes the clickable element an interactive element, but doesn't add
alt text and makes it not-obvious that you can click the elefriend.  On
one hand, this goes against good practice; on the other hand, it's not
*supposed* to be obvious that you can click the elefriend.

Also lay some groundwork needed to interactively change the
glitchfriend.

The codebase uses "elefriend" because it's shorter and didn't require me
to realign the actions in actions/compose.js.  Same idea, though.

Glitched elephant friends kindly provided by @ncls7615.