Enable bundling

[dschwen]

Bundling combines all extension files into a single file. This cuts down on startup time, and is the first step to supporting web-based VSCode.

The main obstacle are the three WASM components in the plugin (tree-sitter, tree-sitter-hit, and hit), which are hard to bundle, as the WASM components are loaded via file system access.

Webpack 5 seems to now have native support for bundling WASM https://webpack.js.org/configuration/experiments/ . This could be a way to achiev this.