feat: initialize typescript

[johncardiologs]

A first jab at introducing ts/tsx to this repo!
cc @jhash

[jho406]

I think this is looking great. Thank you so much.

I want this PR to be sort of a smaller step, so i made comments to keep the babel process while allowing typescript to do checking instead of outputting JS. If you make those smaller changes, i'll merge this. Thanks again!

[johncardiologs]

Hi! Sorry, my mind's been completely elsewhere lately and I left this.

Agreed with the approach of keeping babel -- I made the changes you suggested.
I'll look into the failing tests & trying to get this to compile properly when I next have a chance!

[jho406]

Looks great! Just a few smaller comments. Don't worry about the typechecking errors. We can work on that on another issue. For this first step, I want this merged in so other contributors can start contributing in typescript.

We just have to make sure that the build output is the same.

[jho406]

A rebase onto main would fix those errors.

[johncardiologs]

To compare the build outputs, I ran the builds and diffd the files. Primarily, I saw one added line in the typescript babel build outputs that was appended to the end of every file:

//# sourceMappingURL=data:application/json;charset=utf-8;base64

followed by a string of characters. It seems this corresponds to babel's source map option.

The only other 'true diff' I saw apart from this was the following, where dist/ contains files built via this PR and maindist/ holds files built using the npm run build:index command from branch main:

❯ diff dist/index.js maindist/index.js
4c4
< exports.superglueReducer = exports.pageReducer = exports.mapDispatchToPropsIncludingVisitAndRemote = exports.getIn = exports.fragmentMiddleware = exports.UPDATE_FRAGMENTS = exports.SAVE_RESPONSE = exports.REMOVE_PAGE = exports.GRAFTING_SUCCESS = exports.GRAFTING_ERROR = exports.COPY_PAGE = exports.BEFORE_VISIT = exports.BEFORE_REMOTE = exports.BEFORE_FETCH = exports.ApplicationBase = void 0;
---
> exports.updateFragments = exports.superglueReducer = exports.pageReducer = exports.mapDispatchToPropsIncludingVisitAndRemote = exports.getIn = exports.fragmentMiddleware = exports.UPDATE_FRAGMENTS = exports.SAVE_RESPONSE = exports.REMOVE_PAGE = exports.GRAFTING_SUCCESS = exports.GRAFTING_ERROR = exports.COPY_PAGE = exports.BEFORE_VISIT = exports.BEFORE_REMOTE = exports.BEFORE_FETCH = exports.ApplicationBase = void 0;
10a11
> exports.updateFragments = _reducers.updateFragments;

I'm not entirely sure what could be causing this difference, but it doesn't seem super harmful to me -- though I'm not entirely familiar yet with superglue!

Let me know if there's anything else to fix up, otherwise I think this may be a decent starting point!

[jho406]

I looked through the PR. CI is failing because of eslint. We can ignore that, i'll add another story for that. The output is also slightly different because typescript caught an undefined export updateFragments, which is great!

I had to other comments that i'd like addressed, and i'll merge away! Thanks for working on this.