Potential PWA App

[polygonnedpotato]

What is an issue which you want to solve with your feature request?

Allow the live demo to be installed as a PWA (Progressive Web App).

Allowing the live demo to be installed could include great features such as:

• Offline Support.
• Open text/script files directly from the file system (https://web.dev/file-handling/).
• Open vim.wasm into a clear buffer (without a tryit.js buffer) (https://web.dev/app-shortcuts/).

Describe the solution you'd like

Implement a service worker to cache vim.wasm and the files to run it in the browser.
Add a web manifest to help the browser install it.

Additional context (if any)

Some good tutorials can be found at web.dev (https://web.dev/tags/progressive-web-apps/)