Add array syntax support to validate

[DannyBen]

cc #658

Adds the ability to use arrays for validate in bashly.yml for arguments, flags and environment variables.

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• Preparations
  • Add misisng validation for env_var.validate #661
  • Fix validation running twice for environment variables #662
• Implementation
• Specs
• Example
• JSON Schema
• Documentation - Source / Preview

[meleu]

In my tests it works exactly as I requested. Thanks! ❤️

And I confirm that both forms, string and array, can coexist, like this:

flags:
  - long: --max
    arg: max
    help: Specifies the maximum number to be generated
    default: "32767"
    validate:
      - positive_integer
      - greater_than_min
  - long: --min
    arg: min
    help: Specifies the minimum number to be generated
    default: "1"
    validate: positive_integer