only add prereleases in action

Author: johannes-vogel

.github/workflows/test.yml

@@ -31,6 +31,7 @@ jobs:
           node-version: ${{ matrix.node }}
           cache: 'npm'
 
+      - run: npm add cds-9.0.0.tgz cds-dk-9.0.1.tgz cds-compiler-6.0.2.tgz --save-dev
       - run: npm ci
       - run: npm run lint
       - id: hxe