add framework tests

[mwcz]

We need tests to ensure RHElements continue to work within React, Angular, Vue, etc.

Things to research:

1. for UI-only elements, do visual regression testing to make sure they look right within frameworks
2. for behavioral elements (ex: accordion, tabs), do something like the tests on https://custom-elements-everywhere.com/ to ensure attrs and events work within the framework

[kylebuch8]

Closing in favor of #1011