Adopt jinx reusable workflows for welcome and thank

Adds a hello.yaml that delegates to the jinx reusable workflows so
external contributors get a first-time welcome on open PRs and issues,
and a thank-you on merged PRs.

Requires JINX_APP_ID and JINX_PRIVATE_KEY secrets (org-level or
repo-level) and the jinx[bot] app installed on the repo.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: drmowinckels

.github/workflows/hello.yaml

@@ -0,0 +1,22 @@
+name: Hello on PR or Issue
+
+on:
+  pull_request:
+    types: [opened, closed]
+  issues:
+    types: [opened]
+
+jobs:
+  welcome:
+    if: github.event.action == 'opened'
+    uses: rladies/jinx/.github/workflows/reusable-welcome-contributor.yml@main
+    secrets:
+      JINX_APP_ID: ${{ secrets.JINX_APP_ID }}
+      JINX_PRIVATE_KEY: ${{ secrets.JINX_PRIVATE_KEY }}
+
+  thank:
+    if: github.event_name == 'pull_request' && github.event.action == 'closed' && github.event.pull_request.merged == true
+    uses: rladies/jinx/.github/workflows/reusable-thank-contributor.yml@main
+    secrets:
+      JINX_APP_ID: ${{ secrets.JINX_APP_ID }}
+      JINX_PRIVATE_KEY: ${{ secrets.JINX_PRIVATE_KEY }}