Major README.md cleaning
Additions:
* Add the invidious logo
* Add Quickstart section
* Add relevant links (instance list, documentation, contribute, donate) directly in the header
Badges:
* Add badges for open issues and PRs
* Add "Awesome Humane Tech" badge, as we're listed there
* Move CI passed/translated badges to the top
* Replace the "license feature" with a proper badge
Major section changes:
* Reword titles
* Rewrite features list
* Promote the screenshots sections. People like screenshots!
* Move "donate" to the end, there is a link at the top anyway
* Move section "made with invidious" after all the other invidious related sections + rename it to "Projects using Invidious"
Other fixes:
* Remove useless HTML in the screenshots table
* Remove extra columns in H2 titles
* Remove all useless lines between sections
* Use markdown for git commands + add the staging step
* Promote invidious redirect in "Extensions"
* Update preference screenshots
Fixes:
* Sanitize user-provided content in HTML (Fixes#2193)
* Fix encoding of search query in prev/next pages (Fixes#2229)
* Fix some issues introduced with #2196:
- Fix alignment of all <h3> elements (Move the inline style from the parent to the <h3> element)
- Add missing comma on 'dir' HTML attribute (Typo introduced by PR #2196)
Code cleaning:
* Remove unnecessary 'each_sclice' + 'each' double loop in ECR files
* Clean the player's <source> list generation code (in player.ecr)
Related to #1416, it doesn't really fix the real error, but instead mutes the exception message.
Like explained in #1416, this "exception Error" while flushing the client data doesn't harm the client-server connection. However, this exception message continuously spams the logs and makes debugging and error finding really difficult.
