Make TypeSpec VSCode extension web compatible

To be able to use our extension on `vscode.dev` we need to make it a web extension

Doc: https://code.visualstudio.com/api/extension-guides/web-extensions
Example for LSP: https://github.com/microsoft/vscode-extension-samples/tree/main/lsp-web-extension-sample

There is also the issue that our extension needs the compiler installed locally which I assume wouldn't be possible here. But at least providing the syntax highlighting would be nice

This most likely be able to be done in progressive stages:

- [x] tmgrammar and language config, don't even need anything else from the extension
- [ ] formatter
- [ ] figure out how to pull in some part of the language server where we might not have the packages installed