[WIP] Extension Settings Panel

[mary-lost-her-github]

Description

We added a new Extensions Settings panel to the Settings page; it has three sub-sections for the integration categories (action handlers, contact loaders, and message handlers) and will show toggles for the handlers available within them (based on environment variables). If no handlers are available for an integration category, we hide it. If no integration categories have available handlers, we hide the panel.

Saving works...seems to work, no bugs noticed atm.

Checklist:

• [X] I have manually tested my changes on desktop and mobile
• [ ] The test suite passes locally with my changes
• [X] If my change is a UI change, I have attached a screenshot to the description section of this pull request
• [ ] My change is 300 lines of code or less, or has a documented reason in the description why it’s longer
• [ ] I have made any necessary changes to the documentation
• [ ] I have added tests that prove my fix is effective or that my feature works
• [X] My PR is labeled [WIP] if it is in progress

[mary-lost-her-github]

[mary-lost-her-github]

[crayolakat]

@schuyler1d @mary-lost-her-github This PR is labeled as "WIP". What other TODO items were planned for this PR?

[ibrand]

@schuyler1d and @mary-lost-her-github wanted to bump @crayolakat 's question there ^

[schuyler1d]

I don't think it was fully completed. Maybe @mary-lost-her-github remembers more.