Add tsconfig.json to ease TypeScript development.
Review Request #12735 — Created Nov. 22, 2022 and submitted
When working with
.tsfiles and in-editor checkers, it's nice to have
a tsconfig file to tell those checkers about our environment. It's not
actually used for anything else right now because we compile via babel
and not tsc.
Edited a TypeScript file and no longer saw warnings about non-ES3 stuff.