Update README.md (#24365)

Update README.md (#24365)

1. Add `alt=""` for the Bootstrap logo
2. Replace the HTML entities with the unicode symbols
3. Refactor the badges to something that makes more sense to me
4. Change `Selenium Test Status` alt attribute to `Sauce Labs Test Status`
5. Use shields.io for the peerDependencies badge too
6. Add CSS and JS gzip size badges, shoutout to @ngryman
7. Add a few more trailing slashes to URLs
8. Change link to tooling setup to the website one