ci: Add install yarn step

Signed-off-by: Mihail Mihov <[email protected]>

.github/workflows/saucerswap-v2.yaml

@@ -22,6 +22,9 @@ jobs:
         with:
           node-version: '18.x'
 
+      - name: Setup Yarn
+        run: npm install -g yarn
+
       - name: Get yarn cache directory path
         id: yarn-cache-dir-path
         run: echo "::set-output name=dir::$(yarn cache dir)"