Cache "spring-doc-resources" archive between builds
Cache "spring-doc-resources" archive between builds

This commit configures the Gradle Download plugin that's used a build
step when generating the reference documentation. Here we're making sure
that the task is caching and reusing the resource if it's been
downloaded already.

See gh-23282

spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework