ci: run corepack enable as part of prepare

Author: legobeat

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

@@ -14,6 +14,8 @@ jobs:
         with:
           node-version-file: '.nvmrc'
           cache: 'yarn'
+      - name: Install Yarn
+        run: corepack enable
       - name: Install Yarn dependencies
         run: yarn --immutable