Enable the Slint LSP in the online editor.
The approach is modeled after the Slint Web extension for VSCode, using
the `monaco-languageclient` packet from NPM.
Use the typical src/ setup used in TS projects and split out the code
for the workers into src/worker so that this can get its own
configuration for the typescript compiler. This is necessary as the
web workers run in a more restricted environment as the rest of the
code and because `dom` and `webworker` can not be used together.
Re-use the wasm interpreter from the web site when building for the web
site. It's built & copied in the CI at the same time, and we can
convince rollup to preserve the relative link for production builds,
while aliasing to the local directory for dev builds.
This brings down the editor to ~2.3MB on my machine.
