Add mirror job (#84)

Signed-off-by: eduponz <[email protected]>

.github/workflows/mirror.yml

@@ -0,0 +1,24 @@
+# .github/workflows/mirror.yml
+name: Mirror
+on:
+    push:
+      branches:
+        - '1.2.x'
+
+jobs:
+  mirror_job:
+    runs-on: ubuntu-latest
+    name: Mirror 1.2.x branch to compatible version branches
+    strategy:
+      fail-fast: false
+      matrix:
+        dest_branch:
+          - '1.x'
+    steps:
+    - name: Mirror action step
+      id: mirror
+      uses: eProsima/eProsima-CI/external/mirror-branch-action@v0
+      with:
+        github-token: ${{ secrets.GITHUB_TOKEN }}
+        source: '1.2.x'
+        dest: ${{ matrix.dest_branch }}