fix: Publish WidgetPanelProps

[mofojed]

• Wasn't being published, needed for the DHE refactoring of core plugins
  • Specifically: https://github.com/deephaven-ent/iris/pull/2114/files#diff-536d6ac232028a4ebbafc5ca79bb1a22844488a4b628196e43056379f9326a90R17

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 46.75%. Comparing base (0994c52) to head (1a6e830).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2210   +/-   ##
=======================================
  Coverage   46.75%   46.75%           
=======================================
  Files         694      694           
  Lines       38637    38637           
  Branches     9783     9783           
=======================================
  Hits        18063    18063           
  Misses      20521    20521           
  Partials       53       53           

Flag	Coverage Δ
unit	46.75% <ø> (ø)

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