Add geopolygon to Type enum

[jt274]

Change Summary

Adds the geopolygon to the Type enum. geopolygon field type was added in Typesense v28.0.

This prevents the ArgumentError geopolygon is not a defined Type. when running .collections.retrieve() and a collection has a field of type geopolygon.

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[happy-san]

Thank you for the pull request.