Automatically generate README.md files

**Background info/Context:**
* Each folder containing a set of samples should contain a README.md file (as noted by the [samples' requirements here](https://github.com/GoogleCloudPlatform/kubernetes-engine-samples/blob/main/.github/CONTRIBUTING.md#samples-requirements)).
* See [README.md template here](https://github.com/GoogleCloudPlatform/kubernetes-engine-samples/blob/main/.github/new-samples-templates/README.md).
* This README.md ensures visitors of this repository know:
* where the full tutorials/instructions are for a given sample file.
* what the sample is doing.
* Today, sample authors are expected to manually create these README.md files.

**Feature request:** Ideally, these README.md would be generated automatically. This would reduce the amount of back-and-forth between sample authors, and reduce the work necessary to create new GKE samples.

**Additional info**:
* This feature request was inspired by [this conversation/pull-request](https://github.com/GoogleCloudPlatform/kubernetes-engine-samples/pull/1409#pullrequestreview-2241171066).