This release updates Kotlin version to 2.1.20, while also providing several important improvements and bugfixes.

Improvements

• Implemented encoding null in key and value of a map in Protobuf (#2910)
• Make type argument in JsonTransformingSerializer nullable (#2911)
• Use SPDX identifier in POMs (#2936) (thanks to Leon Linhart)
• Add watchosDeviceArm64 to Okio integration module (#2920) (thanks to Daniel Santiago)
• Update kotlinx-io version to 0.6.0 (#2933) (thanks to Piotr Krzemiński)

Bugfixes

• Fix incorrect enum coercion during deserialization from JsonElement (#2962)
• Supply proper equals(), hashCode(), and toString() for SerialDescriptor() wrapper (#2942)
• Do not encode empty packed collections in protobuf (#2907)