Require Node.js 12.20.0 and move to ESM

README.md

@@ -389,7 +389,8 @@ node-fetch also supports spec-compliant FormData implementations such as [formda
 
 ```js
 import fetch from 'node-fetch';
-import FormData from 'formdata-node';
+import {FormData} from 'formdata-polyfill/esm-min.js';
+import {FormData} from 'formdata-node';
 
 const form = new FormData();
 form.set('greeting', 'Hello, world!');

package.json

@@ -55,7 +55,7 @@
     "coveralls": "^3.1.0",
     "delay": "^5.0.0",
     "form-data": "^4.0.0",
-    "formdata-node": "^3.5.3",
+    "formdata-node": "^3.5.4",
     "mocha": "^8.3.2",
     "p-timeout": "^5.0.0",
     "tsd": "^0.14.0",