Hegel: separate projects for playground and docs

[thecotne]

if we split docs and playground in separate projects docs can be migrated to use hegel as well and also codebase for docs can be much simpler then it is right now

we can have https://try.hegel.js.org or leave https://hegel.js.org/try as is

[thecotne]

also we can replace playground with Theia IDE it's basically highly configurable VS Code Online (i have zero experience with it but most likely it's easier to configure to use language server then barebones Monaco Editor)

[thecotne]

turns out Theia IDE needs backend service to function (as does VS Code Online)

Theia is not designed to run without the backend. It relies on many JSON-RPC services, e.g. to provide languages or filesystem access. In theory, if you can reimplement them when it is possible, but it would be a lot of development and maintenance work.

https://github.com/eclipse-theia/theia/issues/6560#issuecomment-554605358

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but there is monaco-languageclient which should be useful (i have not tried it yet)