feat: Element Call

[hanthor]

Description

Note: this is very much AI generated and not yet thoroughly tested

This implements the widget API inasmuch to get embedded Element Call to work. I'll probably maintain this as a fork, but I'm submitting a PR in case there's any desire for it

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[hanthor]

I have read the CLA Document and I hereby sign the CLA

[hanthor]

This works (barely). I know another implementation is in the works. But I want to keep recommending Cinny to people and the lack of calling is a deal breaker to many