ci: split Automerge and convert Doc to a reusable workflow

Signed-off-by: Unai Martinez-Corral <umartinezcorral@antmicro.com>

.github/workflows/Automerge.yml

@@ -0,0 +1,29 @@
+name: Automerge
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: '0 0 * * *'
+  workflow_dispatch:
+
+jobs:
+
+
+  Pipeline:
+    if: ${{ !(github.event_name != 'pull_request' && github.actor == 'dependabot[bot]') }}
+    uses: ./.github/workflows/Doc.yml
+
+
+  Automerge:
+    needs: Pipeline
+    if: github.event_name == 'pull_request' && github.actor == 'dependabot[bot]'
+    runs-on: ubuntu-latest
+    name: Automerge dependabot PRs
+    permissions:
+      contents: write
+
+    steps:
+
+      - name: Auto-merge Dependabot PR
+        run: GITHUB_TOKEN='${{ github.token }}' gh pr merge '${{ github.event.pull_request.html_url }}' --squash

.github/workflows/Doc.yml

@@ -1,17 +1,11 @@
 name: Docs
 
 on:
-  pull_request:
-  push:
-  schedule:
-    - cron: '0 0 * * *'
-  workflow_dispatch:
+  workflow_call:
 
 jobs:
 
-
   Docs:
-    if: ${{ !(github.event_name != 'pull_request' && github.actor == 'dependabot[bot]') }}
     runs-on: ubuntu-latest
     name: '📓 Docs'
     steps:
@@ -50,17 +44,3 @@ jobs:
           git config --local user.name "GitHub Actions"
           git commit -a -m "update ${{ github.sha }}"
           git push -u origin +HEAD:gh-pages
-
-
-  Automerge:
-    needs: Docs
-    if: github.event_name == 'pull_request' && github.actor == 'dependabot[bot]'
-    runs-on: ubuntu-latest
-    name: Automerge dependabot PRs
-    permissions:
-      contents: write
-
-    steps:
-
-      - name: Auto-merge Dependabot PR
-        run: GITHUB_TOKEN='${{ github.token }}' gh pr merge '${{ github.event.pull_request.html_url }}' --squash