feat(cmd): Add vet Command to CLI Tool

[jshlbrd]

Description

• Adds substation vet to the CLI tool

Motivation and Context

This adds the features of the AWS Lambda validate application to the CLI tool, and follows the conventions of other CLI tool commands (mimicking the go tool). It provides more info on Substation errors than validate by printing the line with the error below the error message, like this:

vet.jsonnet:3 transform 324f1035-10a51b9a: object_target_key: missing required option

    {"type":"hash_sha256","settings":{"id":"324f1035-10a51b9a","object":{"source_key":"foo"}}}

The additional output can be ported to validate using the addition of the stringer on config.go.

How Has This Been Tested?

substation vet was integration tested for a variety of use cases:

• Vetting individual files
• Vetting directories
• Vetting nested directories

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.