fix(build): enable babel-preset-env "bugfixes" compilation

Allows Babel to compile syntax as close as possible to what's supported by the target browsers listed with Browserslist.
See https://babeljs.io/docs/en/babel-preset-env#bugfixes

web3.js/babel.config.json

@@ -1,9 +1,14 @@
 {
   "presets": [
-    ["@babel/preset-env"],
+    [
+      "@babel/preset-env",
+      {
+        "bugfixes": true
+      }
+    ],
     ["@babel/preset-typescript"]
   ],
   "plugins": [
     "@babel/plugin-proposal-class-properties"
   ]
-}
+}