Add Gurklang code evaluation

[gustavwilliam]

We want it to be easy for our members to try out Gurklang, by going to the site. We could host an interface for running Gurklang code.

This would include an area for input during execution, sandboxing it (will already be done for the bot) and a way to edit the code. Once we have the sandboxing done, which will be used for the bot as well, this shouldn’t be too difficult.

[zeeshanok]

We can make it like the Svelte REPL editor
But it should have a dark mode (of course)