Remove unused demo code and convert to typescript

[knewkirk]

Using the demo app inside this repo instead of creating a separate repo to test out features. Looked like that's where this was headed originally, might as well use it.

Doing some housekeeping to get the demo app in a good spot to support the updated requirements:

• convert to typescript because it's a good idea
• remove some unused/unreferenced code because it's messy

[wchan2]

I also made the test_page as a super simple test for the initial client auth integration. I'll leave it up to you and the team whether you guys find that kind of simplicity valuable. If not, we can probably remove that too.

[knewkirk]

Ah yeah I saw that - might come in handy later when we start testing out packaging stuff, might as well leave it in for the time being, might come back to it later. Thanks for the heads up! I think right now I'll keep with the react app just to more closely mirror sdk usage for a potential customer.

fyi I think I'll also just keep all my work on a branch and then put up a PR to master once things are working and in a good spot, don't want to spam y'all with PRs, and probably don't need eyes on everything.