Rewrite everything below the project header to actually describe this
fork instead of a generic copy of upstream's README:
- "About this fork" + list of official Stalwart repositories.
- Corrected the "Nothing is hardcoded" overclaim; Features now lists
what's shared with upstream vs. this fork's own additions, and links
to SCHEMA_DEVIATIONS.md for the tracked exceptions.
- New "Switching your server to this fork's UI" section: how to point
a Stalwart server's WEBAPP application at this fork's release build
via stalwart-cli, and how to switch back.
- Support section now distinguishes fork-specific issues (this repo)
from Stalwart Mail Server support (upstream channels).
- License/Copyright text left untouched; added one line noting fork
changes stay under the same dual license per each file's SPDX header.
The project header block (logo, title, badges) is unchanged.
Steven RYDELL