Establish style guide

[corvus-ch]

Require all jsonnet code to be compliant with jsonnetfmt using the default options. For CI/CD pipelines, the command jsonnetfmt --test **/*.jsonnet can be used, while autoformatting can be done using jsonnetfmt -i **/*.jsonnet.

jsonnetfmt is documented at https://jsonnet.org/learning/tools.html.

For YAML files, we should use yamllint For CI/CD pipelines, the command yamllint -f parsable --no-warnings **/*.yml can be used. For checking before commiting, yamllint **/*.yml will do the trick.

Rule wise, we might opt to make line-length a warning instead an error and or increase the character count from 80 to something like 120. Subject to be discussed.

[corvus-ch]

In a discussion with @simu we figured that there is already a mess with naming of exported things in libraries:

• The Jsonnet standard library uses camelCasing.
• Kapitan is follwing python conventions and uses snake_case.
• The Kube library follows golang convention and uses PascalCasing
• The commodore library does not follow any consistent style and use camelCase and snake_case.

I suggest to follow the lead of Jsonnet and take camelCase as the standard for exported functions and variables.

[corvus-ch]

Consider to also use https://editorconfig.org/. While we can check for this in CI/CD, having an editor config file results in a better developer experience.

[srueg]

Possible ideas: https://github.com/databricks/jsonnet-style-guide

[corvus-ch]

Closed by #88.