Add a step to check the importmap json command on CI (#40)

Author: rmacklin

.github/workflows/ci.yml

@@ -25,3 +25,8 @@ jobs:
       - name: Run tests
         run: |
           bundle exec rake
+
+      - name: Ensure json command prints an importmap
+        run: |
+          cp lib/install/bin/importmap test/dummy/bin/importmap
+          test/dummy/bin/importmap json | jq -e .imports