Show Profile Pictures according to Votes on Poll Options

[timvahlbrock]

Checklist

• Tests written for new code (and old code if feasible).
• New or updated public/exported symbols have accurate TSDoc documentation.
• Linter and other CI checks pass.
• I have licensed the changes to Element by completing the Contributor License Agreement (CLA)

This is an early draft PR. Will need further changes, like:

• Limiting the amount of faces shown per poll option
• Ability to show votes as lists, for cases where face pile might not be sufficient to identify all users
• Tests

[CLAassistant]

All committers have signed the CLA.

[github-actions]

Thanks for opening this pull request, unfortunately we do not accept contributions from the main branch of your fork, please re-open once you switch to an alternative branch for everyone's sanity. See https://github.com/matrix-org/matrix-js-sdk/blob/develop/CONTRIBUTING.md