fix typo

advanded -> advanced
automatic -> automatically

Author: SherylHohman

README.md

@@ -40,7 +40,7 @@ Caveats:
 new ExtractTextPlugin([id: string], filename: string, [options])
 ```
 
-* `id` Unique ident for this plugin instance. (For advanded usage only, by default automatic generated)
+* `id` Unique ident for this plugin instance. (For advanced usage only; by default, automatically generated)
 * `filename` the filename of the result file. May contain `[name]`, `[id]` and `[contenthash]`.
   * `[name]` the name of the chunk
   * `[id]` the number of the chunk