Fixed missed minified builds; (#4805)

* Fixed missed minified builds;
Refactored utils.js;
Refactored `utils.isStandardBrowserEnv()` as a `platform/browser` property;
Added builds size log;

* Replaced `rollup-plugin-filesize` with `rollup-plugin-bundle-size`;

Co-authored-by: Jay <jasonsaayman@gmail.com>

lib/adapters/xhr.js

@@ -58,7 +58,7 @@ export default function xhrAdapter(config) {
       }
     }
 
-    if (utils.isFormData(requestData) && utils.isStandardBrowserEnv()) {
+    if (utils.isFormData(requestData) && platform.isStandardBrowserEnv) {
       requestHeaders.setContentType(false); // Let the browser set it
     }
 
@@ -174,7 +174,7 @@ export default function xhrAdapter(config) {
     // Add xsrf header
     // This is only done if running in a standard browser environment.
     // Specifically not if we're in a web worker, or react-native.
-    if (utils.isStandardBrowserEnv()) {
+    if (platform.isStandardBrowserEnv) {
       // Add xsrf header
       const xsrfValue = (config.withCredentials || isURLSameOrigin(fullPath))
         && config.xsrfCookieName && cookies.read(config.xsrfCookieName);