Update .forgejo/workflows/demo.yaml

.forgejo/workflows/demo.yaml

@@ -21,5 +21,12 @@ jobs:
       - name: Setup deno
         run: https://github.com/denoland/setup-deno@v2
 
+      - name: Test set variable
+        id: build
+        run: deno eval "Promise.resolve().then(_ => console.log(JSON.stringify(Deno.build, null, '\n'))).then(v => "BUILD=" + v).then(console.log)"
+
+      - name: Test get variable
+        run: echo ${{ steps.build.outputs.BUILD }}
+
       - name: Test deno
         run: deno --version