Docs should be embedded in the app, not linked via Github

[brassy-endomorph]

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

On the submission page, the docs about how to upload a PGP key are linked in some help text. The hyperlink goes to a rendered markdown doc hosted on Github. This leaks information.

Describe the solution you'd like

Any docs or help pages we think a user (submitter, recipient) might want to read should be embedded in the app as pre-rendered HTML snippets (no need for a markdown renderer shipped, just do it at build time using dev deps).

This has the advantage of us being able to update docs on main without risk of breaking hyperlinks in apps. It means every app will have correctly version docs always displayed. There will not need to be synchronization between app and doc updates.