feat: CI action / label that makes it easy to cherry-pick just a comm…

…it against cosmos SDK main (cosmos#12478)

## Description

Closes: [#268](osmosis-labs#268)

Adds a Github action that makes it easy to cherry pick commits from a fork PR to main under fork-cherry-pick.yml. The necessity for this PR arises from Mergify / GitHub marketplace currently not having tooling for this kind of action.

How it works:

- Cherry picks the commit of any fork of cosmos-sdk upon a merged PR to main on fork.
- Puts commit into a `pr-patch` branch; makes PR from pr-patch to cosmos:main

---

### Author Checklist

I have...

- [x] included the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [x] added `!` to the type prefix if API or client breaking change
- [x] targeted the correct branch (see [PR Targeting](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#pr-targeting))
- [x] provided a link to the relevant issue or specification
- [x] followed the guidelines for [building modules](https://github.com/cosmos/cosmos-sdk/blob/main/docs/building-modules)
- [x] included the necessary unit and integration [tests](https://github.com/cosmos/cosmos-sdk/blob/main/CONTRIBUTING.md#testing)
- [x] added a changelog entry to `CHANGELOG.md`
- [-] included comments for [documenting Go code](https://blog.golang.org/godoc)
- [x] updated the relevant documentation or specification
- [x] reviewed "Files changed" and left comments if necessary
- [x] confirmed all CI checks have passed

### Reviewers Checklist

*All items are required. Please add a note if the item is not applicable and please add
your handle next to the items reviewed if you only reviewed selected items.*

I have...

- [ ] confirmed the correct [type prefix](https://github.com/commitizen/conventional-commit-types/blob/v3.0.0/index.json) in the PR title
- [ ] confirmed `!` in the type prefix if API or client breaking change
- [ ] confirmed all author checklist items have been addressed 
- [ ] reviewed state machine logic
- [ ] reviewed API design and naming
- [ ] reviewed documentation is accurate
- [ ] reviewed tests and test coverage
- [ ] manually tested (if applicable)

.github/workflows/fork-cherry-pick.yml

@@ -0,0 +1,46 @@
+on:
+  #Set to trigger on every merge to main, not just a closed PR.
+  workflow_dispatch:
+  pull_request_target:
+    branches:
+      - main
+    types: ["closed"]
+
+jobs:
+  cherry_pick:
+    runs-on: ubuntu-latest
+    name: Cherry pick into main
+    if: github.event.pull_request.merged == true
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+      - name: Create PR Patch Branch
+        shell: bash
+        env: 
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+            git config --global user.name "${GITHUB_ACTOR}" #Configs have to be set for pushing the cherry-picked changes onto fork pr-patch branch.
+            git config --global user.email "${GITHUB_ACTOR}@users.noreply.github.com"
+            git remote add upstream https://github.com/cosmos/cosmos-sdk.git
+            git fetch --all                                   # Get the latest code
+            git checkout -b pr-patch upstream/main    # Create new branch based on main branch
+            git cherry-pick ${{github.event.pull_request.head.sha}}  # Cherry pick the latest commit of PR
+            git push -u origin pr-patch               # Push your changes to the remote branch
+      - name: Autocreate PR
+        shell: bash
+        env: 
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          curl --request POST \
+            --url https://api.github.com/repos/cosmos/cosmos-sdk/pulls \
+            --header 'authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' \
+            --header 'content-type: application/json' \
+            --data '{
+              "title": "Automated PR for commit: ${{github.event.pull_request.head.sha}}",
+              "body":"Please merge these awesome changes in!",
+              "head":"${{github.event.pull_request.user.login}}:pr-patch",
+              "base":"main"
+              }' \
+            --fail