Add label metadata when creating a label

[athackst]

Description:
Similar to #76 - It would be neat if we could define the label color and description in the configuration file.

Example:

- changed-files: 
  - any-glob-to-any-file: ['list', 'of', 'globs']
  - any-glob-to-all-files: ['list', 'of', 'globs']
  - all-globs-to-any-file: ['list', 'of', 'globs']
  - all-globs-to-all-files: ['list', 'of', 'globs']
- base-branch: ['list', 'of', 'regexps']
- head-branch: ['list', 'of', 'regexps']
- description: 'Description of label'
- color: 'Color of label'

Justification:
Consistency in labels across repos if using a reusable workflow across repos

Are you willing to submit a PR?
Yes! I have a working branch + tests I can submit if there's interest

[mahabaleshwars]

Hi @athackst,
Thank you for creating this feature request. We will investigate it and provide feedback as soon as we have some updates.