chore: introduce github merit badger workflow (#21898)

See [merit badger readme](https://github.com/kaizencc/github-merit-badger#readme) for an overview of the github action that is introduced in this PR.

The idea is that a "merit badge" will be applied to every incoming PR via label based on prior (successfully merged) contributions to the CDK. The badges are as follows:

- `beginning-contributor`: contributed between 0-2 PRs to the CDK
- `repeat-contributor`: contributed between 3-5 PRs to the CDK
- `valued-contributor`: contributed between 6-12 PRs to the CDK
- `admired-contributor`: contributed between 13-24 PRs to the CDK
- `star-contributor`: contributed between 25-49 PRs to the CDK
- `distinguished-contributor`: contributed 50+ PRs to the CDK

We will **not** label PRs that come from the core team.

Special thanks to @scanlonp and @Tianyi-W if/when this does get merged.

.github/workflows/README.md

@@ -23,6 +23,16 @@ Owner: Core CDK team
 [issue-label-assign.yml](issue-label-assign.yml): Github action for automatically adding labels and/or setting assignees when an Issue or PR is opened or edited based on user-defined Area
 Owner: CDK support team
 
+### PR Labeler
+[pr-labeler.yml](pr-labeler.yml): GitHub action for automatically porting triage labels from issues 
+linked in the PR description to the PR.
+Owner: Core CDK team
+
+### GitHub Merit Badger
+[github-merit-badger.yml](github-merit-badger.yml): GitHub action that adds 'merit badges' to pull
+requests based on the users prior contributions to the CDK.
+Owner: Core CDK team
+
 ## Issue Triggered
 
 ### Closed Issue Message
@@ -44,4 +54,9 @@ Owner: CDK support team
 ### Yarn Upgrader
 [yarn-upgrade.yml](yarn-upgrade.yml): Upgrades yarn dependencies and creates a
 patch file for downloading.
+Owner: Core CDK team
+
+### Issue Reprioritizer
+[issue-reprioritization.yml](issue-reprioritization.yml): GitHub action that labels `p2`
+issues as `p1` if a certain level of community engagement is met.
 Owner: Core CDK team

.github/workflows/github-merit-badger.yml

@@ -0,0 +1,20 @@
+name: github-merit-badger
+on:
+  pull_request_target:
+    types:
+      - opened
+
+jobs:
+  call-action:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - uses: kaizencc/github-merit-badger@main
+        id: merit-badger
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+          badges: '[beginning-contributor,repeat-contributor,valued-contributor,admired-contributor,star-contributor,distinguished-contributor]'
+          thresholds: '[0,3,6,13,25,50]'
+          badge-type: 'achievement'
+          ignore-usernames: '[RomainMuller,rix0rrr,Jerry-AWS,MrArnoldPalmer,iliapolo,otaviomacedo,madeline-k,kaizencc,comcalvi,corymhall,peterwoodworth,ryparker,TheRealAmazonKendra,vinayak-kukreja,Naumel,mrgrain]'