types/README.md: Corrected documentation link (#568)

Signed-off-by: Morten Linderud <morten@linderud.pw>

pkg/types/README.md

@@ -21,4 +21,4 @@ Rekor supports pluggable types (aka different schemas) for entries stored in the
 - RPM Packages [schema](rpm/rpm_schema.json)
   - Versions: 0.0.1
 
-Refer to [Rekor docs](https://docs.sigstore.dev/rekor/pluggable-types) for adding support for new types.
+Refer to [Rekor docs](https://docs.sigstore.dev/rekor/plugable-types) for adding support for new types.