Add artifact.

Author: laech

.github/workflows/main.yml

@@ -13,6 +13,9 @@ jobs:
         with:
           java-version: 1.8
       - run: ./gradlew clean build
+      - uses: actions/upload-artifact@v2
+        with:
+          path: build/distributions/*
 
   build-intellij-2020-2:
     runs-on: ubuntu-latest