Description:
Cache the Maven distribution downloaded by the official Maven Wrapper.

The cache key should probably be derived from the .mvn/wrapper/maven-wrapper.properties file (see documentation), similar to how it is done already for the Gradle Wrapper.

The directory to cache is ~/.m2/wrapper/dists (see documentation).

Justification:
Without caching, projects using the Maven Wrapper would have to download the Maven distribution (~8MB) every time the project is built.

For Gradle the setup-java action already supports caching the Gradle distribution downloaded by the wrapper:

Are you willing to submit a PR?

Probably not