Feature request: allGeneratedPositionsFor

[connor4312]

The source-map library has a function, allGeneratedPositionsFor, which gets all candidate positions for the given source locations. I couldn't see to find a similar function in this library.

[jridgewell]

I don't have time to implement this right now, but it should be simple to add. The core behavior is already implemented for generatedPositionFor. We'd need:

1. Change traceSegmentInternal to return an index instead of a segment.
2. Extract the common parts of generated segment finding into a helper
3. Slice from the segment index until we hit a non-matching segment.

[jridgewell]

Closed by #19