Add option to mark issues that wasn't reported via issue forms

[jamacku]

Type of issue

Feature Request

Description

As discussed in systemd/systemd#23968 (comment) it would be useful to be able to mark issues that bypassed issue form.

/cc @evverx

Describe the solution you'd like

Introduce new optional input that would take name of label, which would be set when issue forms were bypassed.

# ...

mark-non-issue-forms-issues:
  required: false
  default: ''
  description: Name of label that will be set when issue form was bypassed by using `Create and empty issue` or using some other way.

# ...

[jamacku]

Blocked by: stefanbuck/github-issue-parser#26