Fix stamps not being correctly detected

[irgendeinich]

Details

We missed a case for converting the instant stamp type to our native annotation type enum. This lead to certain functions not working with stamp annotations.

Acceptance Criteria

• When approved, right before merging, rebase with master and increment the package version in package.json, package-lock.json, samples/Catalog/package.json, and samples/NativeCatalog/package.json (see example commit: 1bf805f).
• Create a new release (and tag) with the new package version (see https://github.com/PSPDFKit/react-native/releases).

[radazzouz]

LGTM 👍 Nice catch! I took the liberty to fix it for iOS in 8001ede

[radazzouz]

As agreed with @irgendeinich in Slack, I am merging this PR to publish a new release.