Shareable URL for the Effekt playground

[jiribenes]

It would be really nice if we could share code written on the Effekt playground.
The link can be really huge, that's fine, this should be client only.

Something like https://effekt-lang.org/quickstart.html?repl=<short base64-encoded string>?edit=<long base64-encoded string> would enter the text into the editor and REPL.
As a bonus, do the other direction automagically: modify the URL based on the editor (& REPL) state on every edit.
And add a "Link 🔗" button somewhere.

Maybe the base64 encoding is a bad idea, perhaps it's better to use a different encoding.