Fix issue of referencing process object on browser (#778)

This commit does type-check first to avoid referencing the process
object to prevent type issues when using the yorkie-js-sdk in a web
browser via a CDN, etc.

src/devtools/index.ts

@@ -99,7 +99,10 @@ export function setupDevtools<T, P extends Indexable>(
   doc: Document<T, P>,
 ): void {
   // NOTE(hackerwins): For production builds, or when running in Node.js, do nothing.
-  if (process.env.NODE_ENV === 'production' || typeof window === 'undefined') {
+  if (
+    (typeof process !== 'undefined' && process.env.NODE_ENV === 'production') ||
+    typeof window === 'undefined'
+  ) {
     return;
   }