[Fix]: specify working directories in workflow files

.github/workflows/deploy.yml

@@ -31,6 +31,7 @@ jobs:
           cache-dependency-path: "package-lock.json"
 
       - name: Deploy
+        working-directory: ./infrastructure
         run: |
           npm ci
           npx cdk deploy --require-approval never -O output.js

.github/workflows/post-cdk-diff.yml

@@ -27,13 +27,15 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Run `cdk diff`
+        working-directory: ./infrastructure
         run: |
           npm install
           echo '# cdk diffの結果' > cdk-diff-result.txt
           npx cdk diff >> cdk-diff-result.txt
 
       - name: Post a comment
         uses: actions/[email protected]
+        working-directory: ./infrastructure
         with:
           script: |
             const fs = require('fs')