Added workflow to update the homebrew formula

Author: vetlewi

.github/workflows/ci.yml

@@ -0,0 +1,17 @@
+on:
+  push:
+    tags: 'v*'
+
+jobs:
+  homebrew:
+    name: Bump Homebrew formula
+    runs-on: ubuntu-latest
+    steps:
+      - uses: mislav/bump-homebrew-formula-action@v3
+        with:
+          homebrew-tap: 'vetlewi/homebrew-formula'
+          formula-name: 'xia2tree'
+          formula-path: '/'
+        env:
+          # the personal access token should have "repo" & "workflow" scopes
+          COMMITTER_TOKEN: ${{ secrets.COMMITTER_TOKEN }}