[api-minor] Convert markInfo to return data in a Map

[Snuffleupagus]

Note: This functionality isn't currently used in the default viewer.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.19%. Comparing base (c3257df) to head (16b94d1).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #21834      +/-   ##
==========================================
- Coverage   90.19%   90.19%   -0.01%     
==========================================
  Files         264      264              
  Lines       67298    67297       -1     
==========================================
- Hits        60702    60698       -4     
- Misses       6596     6599       +3     

Flag	Coverage Δ
browsertest	66.30% <0.00%> (+0.01%)	⬆️
fonttest	8.92% <ø> (ø)
integrationtest	69.41% <0.00%> (-0.02%)	⬇️
unittest	58.38% <100.00%> (-0.01%)	⬇️
unittestcli	56.94% <100.00%> (-0.02%)	⬇️

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[timvandermeij]

Thanks!