[Feature]: Alert Notifications through Matrix

### User story

I want to use matrix for notifications

### Game

Valheim

### Linux distro

Ubuntu 22.04

### Command

command: send

### Further information

I would like to use matrix as i don't use discord (Cannot chat or post there on the lgsm-server until i give the phonenumber to discord. Somewhat owned by tenent, a chinese company btw.) or rocketchat or slack or telegram for example. I read https://github.com/GameServerManagers/LinuxGSM/issues/1321 this thread but its locked so i cannot add it there.

Protocol: Matrix https://matrix.org/
Server: Synapse (probably not really important for you)
Client: There are some, the most used currently is https://element.io/

Documentation for Synapse is there https://matrix-org.github.io/synapse/latest/welcome_and_overview.html
Documentation for Matrix is there https://matrix.org/docs/chat_basics/matrix-for-im/

As you use python as well, it might be worth checking out https://plugins.octoprint.org/plugins/Octoslack/ or https://plugins.octoprint.org/plugins/matrix_notifier/ - i use the first one already for printing-jobs.

What might help as well, rocketchat seems to use matrix as protocol as well? https://matrix.org/blog/2022/05/30/welcoming-rocket-chat-to-matrix/ and on their site as well https://docs.rocket.chat/use-rocket.chat/workspace-administration/settings/federation/matrix-bridge

Edit: Just in case someone searching here for a room there, i created an unofficial room https://matrix.to/#/#lgsm:matrix.org