Add support for E2E encrypted rooms

[ASoTNetworks]

Currently the bot will send unencrypted messages to an encrypted room which defeats the purpose of the room.

It would be nice if the bot can support sending of encrypted messages.

[jooola]

This needs additional research, but I think this would require the webhook to embed a few libraries (crypto + matrix client) and this is not possible.

Maybe such feature could land in a dedicated alert script, as it allow more advanced logic and libraries than a webhook.

[murlock1000]

Implemented E2EE Matrix message notifications for Zabbix by using the script media type. Github repo: https://github.com/murlock1000/zabbix-matrix-script
Help on improvements appreciated :)