Fix plugin release action (#27)

Author: buildbreaker

.github/workflows/release.yml

@@ -46,15 +46,18 @@ jobs:
   plugin:
     runs-on: ubuntu-latest
     steps:
-    - name: sha256
-      run: |
-        make buildplugin
-        sha256sum ./protoc-gen-connect-kotlin/build/libs/protoc-gen-connect-kotlin.jar >> sha256.txt
-    - name: Publish GitHub artifacts
-      uses: softprops/action-gh-release@v1
-      with:
-        generate_release_notes: true
-        append_body: true
-        files: |
-          ./protoc-gen-connect-kotlin/build/libs/protoc-gen-connect-kotlin.jar
-          sha256.txt
+      - uses: actions/checkout@v3
+      - name: Validate Gradle Wrapper
+        uses: gradle/wrapper-validation-action@v1
+      - name: sha256
+        run: |
+          make buildplugin
+          sha256sum ./protoc-gen-connect-kotlin/build/libs/protoc-gen-connect-kotlin.jar >> sha256.txt
+      - name: Publish GitHub artifacts
+        uses: softprops/action-gh-release@v1
+        with:
+          generate_release_notes: true
+          append_body: true
+          files: |
+            ./protoc-gen-connect-kotlin/build/libs/protoc-gen-connect-kotlin.jar
+            sha256.txt