A builder image for use with gitea act runner

• node - this is the base image for runners
• docker - for building and pushing docker images with automated workflows

When registering a runner, include a label for this image.

When you register your runner, you will be prompted for your labels. Example:

INFO Enter the runner labels, leave blank to use the default labels (comma-separated, for example, ubuntu-20.04:docker://node:16-bullseye,ubuntu-18.04:docker://node:16-buster,linux_arm:host):
ubuntu-latest:docker://rexypoo/builder:latest,ubuntu-22.04:docker://rexypoo/builder:latest,ubuntu-20.04:docker://rexypoo/builder:latest,ubuntu-18.04:docker://node:16-buster

In docker-compose.yml include the environment variable GITEA_RUNNER_LABELS as follows:

services:
  runner:
    image: gitea/act_runner
    environment:
      GITEA_RUNNER_LABELS: "ubuntu-latest:docker://rexypoo/builder:latest,ubuntu-22.04:docker://rexypoo/builder:latest,ubuntu-20.04:docker://rexypoo/builder:latest,ubuntu-18.04:docker://node:16-buster"

Include the environment variable GITEA_RUNNER_LABELS

docker run [...] -e GITEA_RUNNER_LABELS="ubuntu-latest:docker://rexypoo/builder:latest,ubuntu-22.04:docker://rexypoo/builder:latest,ubuntu-20.04:docker://rexypoo/builder:latest,ubuntu-18.04:docker://node:16-buster" gitea/act_runner

I've included the ubuntu-18.04 label so that my gitea instance can build the builder, even if no builder image exists. See .gitea/worflows/docker-publish.yml for specifics of this automated build.