chore: Clarify usage of window fields in IPC.js

Resolves these eslint errors:

/puter/src/IPC.js
    53:69  error  'appCallbackFunctions' is not defined                no-undef
    55:9   error  'appCallbackFunctions' is not defined                no-undef
    57:16  error  'appCallbackFunctions' is not defined                no-undef
    81:33  error  'window_for_app_instance' is not defined             no-undef
    84:27  error  'iframe_for_app_instance' is not defined             no-undef
   105:48  error  Empty block statement                                no-empty
   180:18  error  'api_origin' is not defined                          no-undef
   190:44  error  'auth_token' is not defined                          no-undef
   194:21  error  'logout' is not defined                              no-undef
   207:18  error  'api_origin' is not defined                          no-undef
   216:44  error  'auth_token' is not defined                          no-undef
   220:21  error  'logout' is not defined                              no-undef
   239:18  error  'api_origin' is not defined                          no-undef
   248:44  error  'auth_token' is not defined                          no-undef
   252:21  error  'logout' is not defined                              no-undef
   268:13  error  'is_auth' is not defined                             no-undef
   309:13  error  'is_auth' is not defined                             no-undef
   348:27  error  'window_for_app_instance' is not defined             no-undef
   360:27  error  'window_for_app_instance' is not defined             no-undef
   576:35  error  'uuidv4' is not defined                              no-undef
   582:9   error  'launch_app' is not defined                          no-undef
   597:37  error  'appdata_path' is not defined                        no-undef
   629:12  error  'appdata_signatures' is not defined                  no-undef
   633:23  error  'appdata_signatures' is not defined                  no-undef
   638:30  error  'appdata_path' is not defined                        no-undef
   647:25  error  'appdata_signatures' is not defined                  no-undef
   664:29  error  'appdata_signatures' is not defined                  no-undef
   682:13  error  'is_auth' is not defined                             no-undef
   717:13  error  'is_auth' is not defined                             no-undef
   745:13  error  'is_auth' is not defined                             no-undef
   773:13  error  'is_auth' is not defined                             no-undef
   783:22  error  'api_origin' is not defined                          no-undef
   793:48  error  'auth_token' is not defined                          no-undef
   797:25  error  'logout' is not defined                              no-undef
   825:13  error  'is_auth' is not defined                             no-undef
   857:36  error  'operation_id' is not defined                        no-undef
   872:41  error  'auth_token' is not defined                          no-undef
   873:41  error  'api_origin' is not defined                          no-undef
   939:45  error  'item_icon' is not defined                           no-undef
   951:33  error  'sort_items' is not defined                          no-undef
   954:29  error  'show_save_account_notice_if_needed' is not defined  no-undef
   998:38  error  'busy_indicator_hide_delay' is not defined           no-undef
  1004:33  error  'busy_indicator_hide_delay' is not defined           no-undef
  1018:37  error  'pictures_path' is not defined                       no-undef
  1020:37  error  'desktop_path' is not defined                        no-undef
  1022:37  error  'documents_path' is not defined                      no-undef
  1024:37  error  'videos_path' is not defined                         no-undef
  1026:37  error  'audio_path' is not defined                          no-undef
  1028:37  error  'appdata_path' is not defined                        no-undef
  1032:13  error  'is_auth' is not defined                             no-undef
  1044:28  error  'operation_id' is not defined                        no-undef
  1059:33  error  'auth_token' is not defined                          no-undef
  1060:33  error  'api_origin' is not defined                          no-undef
  1145:31  error  'iframe_for_app_instance' is not defined             no-undef
  1163:31  error  'window_for_app_instance' is not defined             no-undef
  1178:36  error  'get_apps' is not defined                            no-undef
  1199:11  error  'window_for_app_instance' is not defined             no-undef

Author: AtkinsSJ