Add index.d.ts to debugger and jsfiddle images

Needed for https://skia-review.googlesource.com/c/buildbot/+/768445

Change-Id: Ib26813d9e5715dd0ab9ad91ddb92d86f4f23aeee
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/768617
Reviewed-by: Leandro Lovisolo <lovisolo@google.com>
3 files changed