fix: expose Fiber type from react-reconciler

[mdjastrzebski]

Summary

[Provide a brief description of the changes in this PR]

Type of change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (specify below)

How Has This Been Tested?

[Describe the tests you ran to verify your changes]

Checklist:

• Code follows style guidelines
• Self-review completed
• Code commented where necessary
• Documentation updated
• No new warnings generated
• Tests added/updated and passing
• Code coverage maintained/improved
• Dependent changes merged

Additional Notes:

[Add any additional information or context about the PR here]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.66%. Comparing base (2624f67) to head (b68f790).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #22   +/-   ##
=======================================
  Coverage   70.66%   70.66%           
=======================================
  Files           8        9    +1     
  Lines         242      242           
  Branches       43       43           
=======================================
  Hits          171      171           
  Misses         71       71           

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