Add live stream demo page

[szekelyzol]

Changes are for this Asana task.

Summary:

• Add demo page for "Live streaming from your browser" demo: https://livestream.a.video/
• Update navigation.yaml

[szekelyzol]

@arthemium a warning ⚠️ I think this PR should not be merged yet. There are a few updates needed for the Live stream demo page on a.video:

• Blog link is indirect and outdated
• GitHub link is indirect and outdated
• Safari limitation is no longer present (thread on Slack)

The relevant GitHub repo's description would also benefit from an update:

• The tone / voice does not fit in with the rest of our repos
• The technical details are outdated ⚠️
• Lots of typos:
  • "Note: The RTMP endpoint in the code is streaming into my account - and I can see all your videos. Please wear pants. :D"
  • "live straeming"
  • "endpojnt"
  • "Youo'll need"
  • "playabck"
  • "Requiremennts"

These issues are tracked in Asana here.