browser-sdk: Add "meeting_end" embed event

[havardholvik]

Description

Allow customers to take action whenever a meeting has been explicitly ended by the host.

Testing

Check out https://github.com/whereby/pwa/pull/4006. Ensure you have a .env set up with a room url which works with Storybook.

1. yarn dev
2. Visit http://localhost:6006/?path=/story/examples-pre-built-ui--whereby-embed-element-example
3. Join room, then end meeting for all.
4. Verify "Meeting ended: TRUE" is present in the top

Screenshots/GIFs (if applicable)

Checklist

• My code follows the project's coding standards.
• Prefixed the PR title and commit messages with the service or package name
• I have written unit tests (if applicable).
• I have updated the documentation (if applicable).
• By submitting this pull request, I confirm that my contribution is made
  under the terms of the MIT license.

[changeset-bot]

🦋 Changeset detected

Latest commit: 0092158

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@whereby.com/browser-sdk	Minor

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[richtrwhereby]

Works for me with the instructions provided 🚀