Add mxr (#389)

Adds [mxr](https://mxr.sh/), a local-first email client built with
Ratatui. It includes Vim-style navigation, multi-account sync and
full-text search.

Author: bhekanik

README.md

@@ -298,6 +298,7 @@ Aside from those listed here, many other apps and libraries can be easily be fou
 - [JocalSend](https://git.kittencollective.com/nebkor/joecalsend) - Peer to peer local file and data transfer, compatible with [LocalSend](https://github.com/localsend/localsend)
 - [mqttui](https://github.com/EdJoPaTo/mqttui) - MQTT client for subscribing or publishing to topics.
 - [mullvad-tui](https://github.com/d10n/mullvad-tui) - A TUI for Mullvad VPN.
+- [mxr](https://github.com/planetaryescape/mxr) - Local-first email client with Vim-style navigation, multi-account sync, and full-text search.
 - [netscanner](https://github.com/Chleba/netscanner) - Network scanning tool.
 - [nordvpn-tui](https://github.com/Degra02/nordvpn-tui) - A TUI for NordVPN.
 - [oha](https://github.com/hatoo/oha) - Top-like monitoring tool for HTTP(S) traffic.