Create standalone static site for node status page

[hdevalence]

As part of penumbra-zone/penumbra#3522 , where we'd like to have the pd RPC endpoint serve browser-useful content, it would be useful to have a static landing page we can install as the root content.

This should be a static site with the following content:

• A progress bar for the node's sync status, using this RPC to get the SyncInfo data. (It could update on a timer, say 5s). Since this is intended to be served off the RPC, the client should be aimed at the same HTTP endpoint serving the content.
• Below that, a link labeled "Frontend -->" that goes to /app/, where we will have installed minifront.

[grod220]

This seems to be a good candidate to use a react "meta-framework". It will allow us to validate the tech before migrating the web app. Related: #310 (comment)

Also, we should rename "web app" in the repo to "minifront" with this issue so there's no confusion