Github Action to create PR for Podfile.lock (#1097)

Summary:
This PR adds GH action to create PR with the updated Podfile.lock when a new tag is released.

## Changelog

- Add GH action to automatically create PR with updated Podfile.lock.
Pull Request resolved: https://github.com/facebook/flipper/pull/1097

Test Plan: I was not able to test it on a release of tag. But I tested it by triggering the workflow on a push to the branch. It created a PR like [this](https://github.com/facebook/flipper/pull/1110).

Reviewed By: jknoxville

Differential Revision: D21381996

Pulled By: priteshrnandgaonkar

fbshipit-source-id: 2dffa0f71f7e211541728acb06aea5763ae53f47

.github/workflows/publish-pods.yml

@@ -39,3 +39,72 @@ jobs:
         for i in {1..5}; do pod trunk push FlipperKit.podspec --use-libraries --allow-warnings --verbose --skip-import-validation && break || sleep 20; done
       env:
         COCOAPODS_TRUNK_TOKEN: ${{ secrets.COCOAPODS_TRUNK_TOKEN }}
+
+  create_pr:
+    needs: publish_flipperkit_pod
+    runs-on: macos-latest
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Install Dependencies
+      run: pod repo update
+
+    - name: Pod Version
+      run: pod --version
+
+    - name: Update Sample's Podfile.lock
+      run: |
+          cd iOS/Sample/
+          pod update
+          ls
+
+    - name: Update SampleSwift's Podfile.lock
+      run: |
+          cd iOS/SampleSwift/
+          pod update
+          ls
+
+    - name: Update Tutorial's Podfile.lock
+      run: |
+          cd iOS/Tutorial/
+          pod update
+          ls
+
+    # Followed this https://github.com/peter-evans/create-pull-request/blob/master/docs/concepts-guidelines.md#creating-pull-requests-on-tag-push
+    - name: Create a temporary tag branch
+      run: |
+        git config --global user.name 'GitHub'
+        git config --global user.email 'noreply@github.com'
+        git checkout -b temp-${GITHUB_REF:10}
+        git push --set-upstream origin temp-${GITHUB_REF:10}
+
+    - name: Git status
+      run: |
+          git status
+
+    - name: Git diff
+      run: |
+          git diff
+
+    - name: Git branch
+      run: |
+          git branch
+
+    - name: Create PR to Update Podfile.lock
+      uses: peter-evans/create-pull-request@v2
+      with:
+        title: 'Automated: Update Podfile.lock'
+        body: |
+          This is an automated PR to update the Podfile.lock.
+          - Make sure that the Podfile.lock contains latest FlipperKit and Flipper pod versions.
+          - Also make sure that all the dependencies are updated to the latest one.
+          - This is auto-generated by [create-pull-request](https://github.com/peter-evans/create-pull-request)
+        base: 'master'
+        branch-suffix: short-commit-hash
+        labels: automated pr
+      env:
+        GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Delete tag branch
+      run: |
+        git push --delete origin temp-${GITHUB_REF:10}