Add Matrix alerts

alerts/matrix.md

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+# Matrix
+
+![](../.gitbook/assets/matrix_logo.png)
+
+[Matrix](https://matrix.org/) is an open network for secure, decentralized communication that allows to allows other applications to send messages via an API.
+
+## Setup a Matrix Bot
+
+To enable Matrix alerts, it is recommended that you create a new account dedicated to sending alerts. This will act as a bot account. You can create an account on your preferred Matrix server. Once you create your account, you can assign it a friendly name and a [picture](https://raw.githubusercontent.com/n194/LinuxGSM/matrix-alert/lgsm/data/alert_discord_logo.jpg).
+
+Next, you will have to get an access token for the account. 
+- Element: https://t2bot.io/docs/access_tokens/
+- API: https://www.matrix.org/docs/guides/client-server-api#login
+
+Enter your homeservers and the token in the [LinuxGSM config](../configuration/linuxgsm-config.md).
+
+```text
+   # Matrix Alerts | https://docs.linuxgsm.com/alerts/matrix
+   matrixalert="on"
+   matrixhomeserver="matrix.org"
+   matrixtoken="swt_a219dC4ib5T_QjAZsnEPpJLDNWSeDfk_8vj1Uw"
+   matrixroom=""
+```
+
+## Matrix room ID
+
+The room ID is used to identify where the alert is being sent. Each room has its own unique ID.
+
+To obtain the room ID in Element, go to the room settings, go to the advanced tab and copy the internal room ID.
+
+Add the room id to the [LinuxGSM config](../configuration/linuxgsm-config.md).
+
+```text
+   # Matrix Alerts | https://docs.linuxgsm.com/alerts/matrix
+   matrixalert="on"
+   matrixhomeserver="matrix.org"
+   matrixtoken="swt_a219dC4ib5T_QjAZsnEPpJLDNWSeDfk_8vj1Uw"
+   matrixroom="!ygKaCNBxvTMUSagvZdz:matrix.org"
+```
+
+### Send Test Alert
+
+Finally, test that everything correctly works by sending a test alert. You will now receive a message from the bot directly or to a chosen group.
+
+```text
+./gameserver test-alert
+```