Add black formatting workflow

.github/workflows/format_black.yml

@@ -0,0 +1,35 @@
+# This workflow will checkout the branch of the PR, apply black formatting and commit the result to the PR. Does not work for forks.
+
+name: Format black
+
+on:
+  pull_request:
+    types: [labeled]
+
+jobs:
+  build:
+    if: contains(github.event.pull_request.labels.*.name, 'format_black' )
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        token: ${{ secrets.DEPENDABOT_WORKFLOW_TOKEN }}
+        ref: ${{ github.event.pull_request.head.ref }} # Check out the head of the actual branch, not the PR
+        fetch-depth: 0 # otherwise, you will fail to push refs to dest repo
+    - name: format black
+      uses: psf/black@stable
+      with:
+        options: ""
+        src: "./pylammpsmpi"
+    - name: commit
+      run: |
+        git config --local user.email "pyiron@mpie.de"
+        git config --local user.name "pyiron-runner"
+        git commit -m "Format black" -a
+    - name: push
+      uses: ad-m/github-push-action@master
+      with:
+        github_token: ${{ secrets.DEPENDABOT_WORKFLOW_TOKEN }}
+        branch: ${{ github.event.pull_request.head.ref }}