Update config.ts to add maxTokens default

OpenAI maxTokens is 2000000.  Having this as a default may help new users

Author: mcoliver

config.ts

@@ -5,4 +5,5 @@ export const defaultConfig: Config = {
   match: "https://www.builder.io/c/docs/**",
   maxPagesToCrawl: 50,
   outputFileName: "output.json",
+  maxTokens?: 2000000,
 };