Make assets available in a standalone directory to serve hydrogen-view-sdk/assets/

[MadLittleMods]

Is your feature request related to a problem? Please describe.

It's hard to serve the static assets like the SVG icons and fonts because they are spread out amongst the rest of the package files in the root package directory.

Describe the solution you'd like

• Have all assets available to serve under hydrogen-view-sdk/assets/
  • Add "./assets/": "./asset-build/assets/" to the list of package.json exports
  • Don't delete and move the asset-build directory in the build script
• Also add an empty index.js like hydrogen-view-sdk/assets/index.js so require.resolve('hydrogen-view-sdk/assets/') can resolve the path properly.
• Then assets can simply be served like app.use(express.static(path.dirname(require.resolve('hydrogen-view-sdk/assets/'))));

In order to avoid the following deprecation notice, we probably want to use this instead:

• Add "./assets/*": "./asset-build/assets/*" to the list of package.json exports
• require.resolve('hydrogen-view-sdk/assets/index.js')

(node:46028) [DEP0148] DeprecationWarning: Use of deprecated folder mapping "./assets/" in the "exports" field module resolution of the package at C:\Users\MLM\Documents\GitHub\element\matrix-public-archive\node_modules\hydrogen-view-sdk\package.json.
Update this package.json to use a subpath pattern like "./assets/*".

Describe alternatives you've considered

Vite does have SSR support for running in Node.js but I didn't want to dive into all of that complexity yet as it's not necessary. Might switch over though.

Additional context

This makes hydrogen-view-sdk easier to work with if you're not using Vite although the SDK specifies that only Vite is supported though: "Currently, only vite is supported" -- doc/SDK.md.

hydrogen-view-sdk currently doesn't even support CommonJS yet because of a Vite bug. Re-introducing CommonJS support is tracked by #686

https://github.com/vector-im/hydrogen-web/blob/0ff1a01b429799e5ade9d21e0186ab0980b4add0/scripts/sdk/create-manifest.js#L5-L26