Wasm Demo Frontend Framework

[QnnOkabayashi]

The wasm demo is currently written in vanilla TypeScript. This makes it difficult to add new demos to the webpage, since all the HTML and TS pieces have to be added manually, and rules for what to update when an input is updated are encoded by hand.

A frontend framework like Svelte would simplify this process, and make adding new demos as simple as "use these inputs, have them call these Diplomat bindings, and show the output here."

Currently, the demo is generated for every PR, so this would ideally enable authors to easily add a demo for their new feature that the reviewers could interact with in real time.