Some improvements

- Use classes
- Split buildx/builder modules
- Additional tests

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

jest.config.ts

@@ -1,4 +1,5 @@
 process.env = Object.assign({}, process.env, {
+  GITHUB_REPOSITORY: 'docker/test-docker-action',
   RUNNER_TEMP: '/tmp/github_runner',
   RUNNER_TOOL_CACHE: '/tmp/github_tool_cache'
 }) as {