fix: expose union type of shapes that have a fwhm

[targos]

There are packages such as ml-gsd that depend on the existence of this field on all treated shapes.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.84%. Comparing base (2e8336e) to head (01aa4c1).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #108   +/-   ##
=======================================
  Coverage   96.84%   96.84%           
=======================================
  Files          24       24           
  Lines        1171     1171           
  Branches      262      262           
=======================================
  Hits         1134     1134           
  Misses         36       36           
  Partials        1        1           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.