Outline to call a person (request a voice or video session) using their website:
- tantek writes a post on his site that says "hey aaronpk, do you have a minute to talk? https://talky.io/ttk"
- tantek's server sends a webmention to mine for that link
- my server notifies my phone via a push notification (possibly via mention-app)
- I see the message, click the talky URL, and we're in a video call
Additionally, this could happen with private posts so the talky URL is only visible to the two of us.