docs: point first-time users to docs

[escapedcat]

Description

Should fix #471

Usage examples

New output message looks liek this:

✖   subject may not be empty [subject-empty]
✖   type may not be empty [type-empty]
✖   found 2 problems, 0 warnings
    (Need help? -> https://github.com/marionebl/commitlint#what-is-commitlint)

How Has This Been Tested?

Updated tests for format

Types of changes

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

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
  I think master is still broken for now. Need to check this in another PR.