feat: commment on libsession constants

give context that CONSTANTS is not a object but an immediately invoked
function

ts/session/utils/libsession/libsession_constants.ts

@@ -1,5 +1,6 @@
 import { CONSTANTS, ConstantsType } from 'libsession_util_nodejs';
 
+// NOTE CONSTANTS is an immediately invoked function that returns the libsession constants object
 const { CONTACT_MAX_NAME_LENGTH, BASE_GROUP_MAX_NAME_LENGTH, GROUP_INFO_MAX_NAME_LENGTH } =
   CONSTANTS;