Debug ID: Define for Index Source Map

[lforst]

Debug IDs should probably also be supported on Index Source Maps so we should point out the debugId field in the Index Source Maps section.

[lukesandberg]

turbopack uses index source maps to avoid remapping everything.

I assume this should just work with tools like sentry, but having it codified in the spec here would be nice.

[szuend]

We discussed this in the recent TG4 meeting. I added test cases for this here tc39/source-map-tests#36 (I'll also add a case where only the sections have a debug ID and expect the ID to not show up in the final record).

@lforst Do you plan to update the Debug ID spec PR (#207) or do you want me to take it over?

[lforst]

@szuend that sounds good to me! Feel free to take over the PR (or even create a new one). I think a blocker on the PR in general is that we still need to iron out the comment parsing. Maybe it's an option to split out the "field part" and the "parsing part" but they feel atomic in a way.