chore: add set milestone action (#391)

See [#401 - Automatically set milestone at issues when
closed](open-component-model/ocm-project#401)
for more information. Now with reuse of central managed action.

Co-authored-by: ocmbot[bot] <125909804+ocmbot[bot]@users.noreply.github.com>

.github/workflows/milestone.yaml

@@ -2,25 +2,15 @@ name: Set milestone
 on:
   issues:
     types:
-      - closed
+    - closed
   pull_request:
     types:
-      - closed
+    - closed
+
 jobs:
   set_milestone:
-    name: Set milestone
-    runs-on: ubuntu-latest
+    uses: open-component-model/.github/.github/workflows/milestone.yml@main
+    secrets: inherit
     permissions:
       issues: write
-      pull-requests: write    
-    steps:
-      - name: Set milestone on issue
-        if: github.event.issue.state_reason == 'completed'
-        run: gh issue edit ${{ github.event.issue.number }} --milestone "$(date +"%Y-Q%q")" --repo ${{ github.repository }}
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-      - name: Set milestone on pull request
-        if: github.event.pull_request.merged == true
-        run: gh pr edit ${{ github.event.pull_request.number }} --milestone "$(date +"%Y-Q%q")" --repo ${{ github.repository }}
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+      pull-requests: write