Fixes#67
Add support for overriding disk cache files for multiple modules in the repository.
* Add a new input `disk-cache-files` in `action.yml` to specify custom disk cache files.
* Update `config.js` to handle the new `disk-cache-files` input and override the `diskCache.files` array if provided.
* Update the documentation in `README.md` to include the new `disk-cache-files` input and provide examples of its usage.
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For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/bazel-contrib/setup-bazel/issues/67?shareId=XXXX-XXXX-XXXX-XXXX).
Like BUILD file changes, changes to workspace dependencies can
significantly affect the contents of the disk cache. Prior to this
change, upreving dependencies wasn't itself sufficient to update the
disk cache, resulting in repeatedly rebuilding dependencies until some
subsequent commit happened to modify BUILD files.
