* [typescript] add build support for typescript
* [typescript] working lint and build
* [typescript] refactor SupersetClient to TS
* [typescript][connection] leverage RequestInit types when relevant
* [typescript][connection] callApi.js => callApi.ts
* [typescript][connection] remaining .js => .ts
* [typescript][connection] add and export src/types.ts, refactor things, convert test to .ts and fix
* [typescript] build:ts only in typescript-containing packages