Restore yarn install and ts

Author: hsubox76

.github/workflows/check-changeset.yml

@@ -22,4 +22,4 @@ jobs:
       run: yarn ts-node-script scripts/check_changeset.ts
       id: check-changeset
     - name: Read output
-      run: echo env.MISSING_PACKAGES
+      run: echo $MISSING_PACKAGES