Add `spotguide lint` command

[orymate]

Check things like below in the git repo of the current working directory:

• Every Spotguide file must be within a .banzaicloud directory
• Must contain a README.md file providing a simple description/documentation for the Spotguide
• Must contain an icon.svg file
• Must contain a CI/CD configuration template in pipeline.yaml
• Must contain Spotguide configuration (eg. name) and questionnaire in spotguide.yaml

[orymate]

@sagikazarmark