ci: add GitHub Actions workflows for NPM publishing and CI builds

Author: ahnv

.github/workflows/ci.yaml

@@ -0,0 +1,37 @@
+name: Node CI
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  pack:
+    if: github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name != github.event.pull_request.base.repo.full_name
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: ⬇️  Check out code
+        uses: actions/checkout@v4
+
+      - name: 🟢 Enable Corepack
+        run: corepack enable
+
+      - name: 🟢  Set up Node 20
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20.x
+          cache: yarn
+
+      - name: 📦  Install deps, build, pack
+        run: |
+          yarn install --frozen-lockfile
+          yarn build
+          yarn pack --out %s-%v.tgz
+        env:
+          CI: true
+
+      - name: 📤  Upload package artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: strapi-plugin-imagekit-package
+          path: strapi-plugin-imagekit-*.tgz