Publish as web extension

[anderseknert]

Web extensions are extensions that can be installed in the web interface for VS Code, such as presented in GitHub et. al.

While we can't do things like calling out to the OPA binary in this context, we could still provide basic features like syntax highlighting.

Note that extensions can be published both as a "desktop" version and a web one, which is what we'll want to do here. We don't want to limit the capabilities of the desktop one, so this would be a new additional part of the project.

More info here: https://code.visualstudio.com/api/extension-guides/web-extensions

(It's even possible to run a language server inside of a web worker, so we could compile Regal to Wasm (as @srenatus previously demonstrated) or if not that, at least the Regal policies, and have linting enabled too. But let's start with the basics)