chore: upgrade to node 20

.github/workflows/build.yml

@@ -52,7 +52,7 @@ jobs:
           file_name_in_stack_trace: true
       - uses: actions/setup-node@v4
         with:
-          node-version: 16
+          node-version: 20
           cache: npm
       - run: npm install
       - run: npm run eslint

.npmrc

@@ -0,0 +1 @@
+save-exact = true

action.yml

@@ -49,5 +49,5 @@ outputs:
      description: 'the test outcome, either `success` or `failure`'
 
 runs:
-  using: 'node16'
+  using: 'node20'
   main: 'dist/index.js'