Add ability to specify an include filter for the files to be purged

[tripodsan]

suggest an input property 'include':

on: push

jobs:
  ci_trigger:
    runs-on: ubuntu-latest
    name: Clear helix pages cache
    steps:
      - name: Trigger
        id: trigger
        uses: adobe-rnd/github-purge-cache-action@master
        with:
          repo-token: ${{ secrets.MY_GITHUB_TOKEN }}
          include:
            - /scripts*
            - /styles*

the filtering should use https://www.npmjs.com/package/glob

[davidnuescheler]

looking at all the helix pages repos i am not sure that would be required initially. there may definitely be edge cases where people have commits with many files that have no representation on the public facing website, but i can't see those yet.
so i would suggest we hold off with that until we find some issues... all things considered, the potential purging of things that were never in the cache is relatively low overhead.