fix: Performance 25% or so faster in chrome/v8 for mse

Author: robertleeplummerjr

browser.js

@@ -6,7 +6,7 @@
  *   license: MIT (http://opensource.org/licenses/MIT)
  *   author: Heather Arthur <fayearthur@gmail.com>
  *   homepage: https://github.com/brainjs/brain.js#readme
- *   version: 1.4.7
+ *   version: 1.4.8
  *
  * acorn:
  *   license: MIT (http://opensource.org/licenses/MIT)
@@ -5347,7 +5347,7 @@ function mse(errors) {
   // mean squared error
   var sum = 0;
   for (var i = 0; i < errors.length; i++) {
-    sum += Math.pow(errors[i], 2);
+    sum += errors[i] * errors[i];
   }
   return sum / errors.length;
 }

browser.min.js

@@ -1,7 +1,7 @@
 {
   "name": "brain.js",
   "description": "Neural network library",
-  "version": "1.4.7",
+  "version": "1.4.8",
   "author": "Heather Arthur <fayearthur@gmail.com>",
   "repository": {
     "type": "git",

dist/utilities/mse.js

@@ -2,7 +2,7 @@ export default function mse(errors) {
   // mean squared error
   let sum = 0;
   for (let i = 0; i < errors.length; i++) {
-    sum += Math.pow(errors[i], 2);
+    sum += errors[i] * errors[i];
   }
   return sum / errors.length;
 }