ci: jest maxWorkers 사용

Author: drakang4

.github/workflows/ci.yaml

@@ -129,9 +129,13 @@ jobs:
 
       - run: npm ci
 
+      - name: Get number of CPU cores
+        id: cpu-cores
+        uses: SimenB/github-actions-cpu-cores@v1
+
       - name: Generate coverage report
         id: test
-        run: npm run test:coverage -- --ci --reporters github-actions --reporters summary --runInBand
+        run: npm run test:coverage -- --ci --reporters github-actions --reporters summary --maxWorkers ${{ steps.cpu-cores.outputs.count }}
 
       - name: Notify testing failure
         if: failure() && steps.test.outcome == 'failure'