Add automated testing of changes in .github/workflows

[anoronh4]

A few enhancements

• changing any files under .github/workflows will result in building and pushing testapp/0.0.2 (github workflow for testing github action #15)
• separate hadolint action into a different job because it does not need to be run with the docker (separate hadolint from image building jobs #17)
• dev workflow now supports running the github workflow using act. An example to command to run act is: act -s MSK_JFROG_USERNAME=<jfrogusername> -s MSK_JFROG_TOKEN=<jfrogtoken> -s GITHUB_TOKEN=<mytoken> --workflows .github/workflows/dev-build.yml