adds a step to check for vulnerabilities

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

@@ -21,11 +21,13 @@ jobs:
                 cache: 'npm'
                 cache-dependency-path: '**/package-lock.json'
 
-
             - name: Install dependencies
               run: npm ci
               working-directory: xero-node
 
+            - name: Check for vulnerabilities
+              run: npm audit --exit-code
+
             - name: Run Build
               run: npm run build
               working-directory: xero-node