Improve CI setup (#1752)

Author: markerikson

.codesandbox/ci.json

@@ -0,0 +1,6 @@
+{
+  "sandboxes": ["vanilla", "vanilla-ts"],
+  "node": "14",
+  "buildCommand": "build",
+  "packages": ["."]
+}

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
         uses: actions/checkout@v2
 
       - name: Cache dependencies
-      - uses: actions/cache@v2
+        uses: actions/cache@v2
         with:
           path: .yarn/cache
           key: yarn-${{ hashFiles('yarn.lock') }}