Assert if MODULARIZE factory function is used with new.

Once we start using `async` for for this function then `new` stops
working: emscripten-core#23157.

Using `new` in this was was always an antipattern but there was nothing
stopping users from doing this.

Author: sbc100

ChangeLog.md

@@ -36,6 +36,7 @@ See docs/process.md for more on how version tagging works.
   This paves the way for marking the function as `async` which does not allow
   `new` to be used.  This usage of `new` here was never documented and is
   considered and antipattern. (#23210)
+  considered an antipattern. (#23210)
 - `PATH.basename()` no longer calls `PATH.normalize()`, so that
   `PATH.basename("a/.")` returns `"."` instead of `"a"` and
   `PATH.basename("a/b/..")` returns `".."` instead of `"a"`. This is in line with