enable esm support only above 12.11.0 due to bug in Node ESM impl

Node 12.11.0 has a bug in dealing with dynamic import and type="module"
So I decided to suppress ESM support in Mocha prior to that version, which fixes
the bug

docs/index.md

@@ -1527,7 +1527,7 @@ this means either ending the file with a `.mjs` extension, or, if you want to us
 adding `"type": "module"` to your `package.json`.
 More information can be found in the [Node.js documentation](https://nodejs.org/api/esm.html).
 
-> Mocha supports ES modules only from Node.js v12 and above. Also note that
+> Mocha supports ES modules only from Node.js v12.11.0 and above. Also note that
 > to enable this, you need to add `--experimental-modules` when running
 > Mocha. Last, but not least, the ESM implementation Mocha is not yet
 > stable so given that the specification in Node.js may

lib/utils.js

@@ -843,7 +843,21 @@ exports.defineConstants = function(obj) {
  * @returns {Boolean} whether the current version of Node.JS supports ES Modules in a way that is compatbile with Mocha
  */
 exports.supportsEsModules = function() {
-  return typeof document === 'undefined'
-    ? +process.versions.node.split('.')[0] >= 12
-    : false;
+  if (typeof document !== 'undefined') {
+    return false;
+  }
+
+  var versionFields = process.versions.node.split('.');
+  var major = +versionFields[0];
+
+  if (major >= 13) {
+    return true;
+  }
+  if (major < 12) {
+    return false;
+  }
+  // major === 12
+  var minor = +versionFields[1];
+
+  return minor >= 11;
 };