docs(multiple): add docker cache notes to build-push-to-dockerhub and push-to-gar-docker (#1003)

* docs(multiple): add docker cache notes to build-push-to-dockerhub and push-to-gar-docker

* Apply prettier recommendations

Author: ricky-undeadcoders

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

@@ -1,5 +1,10 @@
 # build-push-to-dockerhub
 
+> [!NOTE]
+> If you are at Grafana Labs:
+>
+> - A docker mirror is available on our self-hosted runners, see [the internal documentation](https://enghub.grafana-ops.net/docs/default/component/deployment-tools/platform/continuous-integration/#docker-caching-in-github-actions) for more info.
+
 This is a composite GitHub Action, used to build Docker images and push them to DockerHub.
 It uses `get-vault-secrets` action to get the DockerHub username and password from Vault.
 

actions/push-to-gar-docker/README.md

@@ -1,7 +1,10 @@
 # push-to-gar-docker
 
 > [!NOTE]
-> If you are at Grafana Labs, follow these steps in the [internal documentation](https://enghub.grafana-ops.net/docs/default/component/deployment-tools/platform/continuous-integration/google-artifact-registry/) to set up a repository before using this action.
+> If you are at Grafana Labs:
+>
+> - Follow these steps in the [internal documentation](https://enghub.grafana-ops.net/docs/default/component/deployment-tools/platform/continuous-integration/google-artifact-registry/) to set up a repository before using this action.
+> - A docker mirror is available on our self-hosted runners, see [the internal documentation](https://enghub.grafana-ops.net/docs/default/component/deployment-tools/platform/continuous-integration/#docker-caching-in-github-actions) for more info.
 
 This is a composite GitHub Action, used to push docker images to Google Artifact Registry (GAR).
 It uses [OIDC authentication](https://docs.github.com/en/actions/deployment/security-hardening-your-deployments/about-security-hardening-with-openid-connect)