Ignore all pull request milestones input

Name: pull-request-ignore-all-milestones
Type: boolean
Default value: false

This input will let you ignore the processing of the pull requests which have a milestone.
This can be useful when you use milestones for triage.

# ...
name: Stale
id: stale
uses: sonia-corporation/stale@latest
with:
  pull-request-ignore-all-milestones: true