Merge pull request #25 from ooade/patch/update-ci-to-use-yarn

Update CI to use yarn

Author: ooade

.github/workflows/build-test-code.yml

@@ -1,4 +1,4 @@
-name: Test code on pull request
+name: PR Action
 
 on:
   pull_request:
@@ -12,6 +12,6 @@ jobs:
       - uses: actions/setup-node@v1
         with:
           node-version: 12
-      - run: npm ci
-      - run: npm test
-      - run: npm run build
+      - run: yarn install --frozen-lockfile
+      - run: yarn test
+      - run: yarn run build