Summary:
`tsconfig.json` has comments, so it is jsonc.
Cf. https://aka.ms/tsconfig.json
Also add tsconfig.json in rootdir and update arclint to ignore
`tsconfig.json`.
Signed-off-by: Yongmin Hong <revi@omglol.email>
Test Plan: Try prettier checks on `tsconfig.json` after merging.
Reviewers: O1 revi & automations, revi
Reviewed By: O1 revi & automations, revi
Differential Revision: https://issuetracker.revi.xyz/D376
