Bash and Zsh completion support for Gradle.

This provides fast tab completion for:

- Gradle tasks for the current project and sub-projects
- Gradle CLI switches (e.g. --parallel)
- Common Gradle properties (e.g. -Dorg.gradle.debug)

It also handles custom default build files, so rootProject.buildFileName =
'build.gradle.kts' is supported.

WWW: https://github.com/gradle/gradle-completion