Frigga

- [ENHANCEMENT] By default, the command `frigga prometheus-apply` (or `frigga pa`) creates a `.prometheus-rules.yml` file. This file contains `relabel_configs`, which makes it easier to copy-paste if necessary.<br>Can be skipped by adding the flag `--skip-rules-file`

- [BUGFIX] Closes 11 - Metrics per dashboard in `.metrics.json` are now fully accurate. It's worth noting that `all_metrics` was working fine, the only thing that didn't work well was the allocation of metrics per dashboards in the `.metrics.json` file. Kudos to mforgues

- [BUGFIX] Closes 7 - enables using private dashboards `gnet_id=null`, since private dashboards don't have a gnet_id

1. Automatically builds the image on DockerHub - https://hub.docker.com/r/unfor19/frigga
- You can't use prompts when using the docker image, must use args, such as `-gurl 123 -gkey 123`
1. Fixed the issue with "query", the scraping is now per string type, hence no more errors
1. Prints corrupted expressions if there are any
1. Testing includes Kubernetes (minikube)

- Added testing with GitHub Actions
- Using docker-compose for running the tests