Add Janus WebRTC Server

[nodiscc]

Thanks for taking the time to suggest an addition to awesome-selfhosted!

Please fill out information below:

# software/janus.yml
name: "Janus"
website_url: "https://janus.conf.meetecho.com/"
source_code_url: "https://github.com/meetecho/janus-gateway"
description: "General-purpose, lightweight, minimalist WebRTC Server."
licenses:
  - GPL-3.0
platforms:
  - C
tags:
  - Communication - Video Conferencing
demo_url: "https://janus.conf.meetecho.com/demos.html"

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