feat(build-push-to-dockerhub): add labels input (#1471)

* feat(build-push-to-dockerhub): add labels input

Allow custom labels to be added to container images.

* fix(build-push-to-dockerhub): remove required

`labels` shouldn't be required.

* feat(build-push-to-dockerhub): copilot feedback

Address suggestions from Copilot.

Author: martincostello

actions/build-push-to-dockerhub/README.md

@@ -53,6 +53,7 @@ jobs:
 | `push`                 | Bool   | Push the generated image (default: `false`)                                                                                                                                                      |
 | `repository`           | String | Docker repository name (**required**)                                                                                                                                                            |
 | `tags`                 | List   | Tags that should be used for the image (see the [metadata-action][mda] for details)                                                                                                              |
+| `labels`               | List   | Labels that should be used for the image (see the [metadata-action][mda] for details)                                                                                                            |
 | `file`                 | String | Path and filename of the dockerfile to build from. (Default: `{context}/Dockerfile`)                                                                                                             |
 | `build-args`           | String | List of arguments necessary for the Docker image to be built.                                                                                                                                    |
 | `target`               | String | Sets the target stage to build                                                                                                                                                                   |

actions/build-push-to-dockerhub/action.yaml

@@ -9,6 +9,10 @@ inputs:
     description: |
       List of Docker images to be pushed.
     required: true
+  labels:
+    description: |
+      List of custom labels to be added to the image.
+    required: false
   context:
     description: |
       Path to the Docker build context.
@@ -106,6 +110,7 @@ runs:
       uses: docker/metadata-action@c1e51972afc2121e065aed6d45c65596fe445f3f # v5.8.0
       with:
         images: ${{ inputs.repository }}
+        labels: ${{ inputs.labels }}
         tags: ${{ inputs.tags }}
 
     # The `context` input is flagged by Zizmor as a [sink]. This means that with