feat: Add preferences cookie URL to import and export preferences

[Fijxu]

Adds a preferences query parameter to the preferences page to import preferences and it also displays and URL to export the preferences to copy and paste it anywhere:

Any suggestions are appreciated because looks kinda off to me.

[unixfox]

The UI is a bit odd. Sounds like a weird "hacker" interface at the end of the preferences page.

[SamantazFox]

Any suggestions are appreciated because looks kinda off to me.

Maybe something like what DDG does?

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You could put the cookie value (JSON) directly, and as for the bookmarklet option, you could pass the various options to /preferences as URL parameters.

By the way, instead of adding a ton of dedicated logic for that in show(), you can simply put the URL query parameters (env.params.query) in the body (env.params.body) and chain a call to the update() handler. A similar thing is done for the download handler in routes/watch.cr.

Maybe offer the option of using redirect.invidious.io as a "portal" for the favorite, so this also works cross instance?