Update README.md with Twilio Video EOL banner

[anna-vasilko]

Update README.md with Twilio Video EOL banner

Contributing to Twilio

All third party contributors acknowledge that any contributions they provide will be made under the same open source license that the open source project is provided under.

• [ ] I acknowledge that all my contributions will be made under the project's license.

Pull Request Details

JIRA link(s):

• AHOYAPPS-0000

Description

A description of what this PR does.

Burndown

Before review

• [ ] Updated CHANGELOG.md if necessary
• [ ] Added unit tests if necessary
• [ ] Updated affected documentation
• [ ] Verified locally with npm test
• [ ] Manually sanity tested running locally
• [ ] Included screenshot as PR comment (if needed)
• [ ] Ready for review

Before merge

• [ ] Got one or more +1s
• [ ] Re-tested if necessary