Make TypeSpec VSCode extension web compatible

[timotheeguerin]

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:

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