Bug description

Compiling esm code cannot be used directly in the bundler module，.e.g:

The Object.assign cant work. Because bundle module is not the same as browser esm.module export variable just only have getter.

Steps to reproduce

1. use binding @external("../test","test")
2. complie esm code

3. I hava a Compatibility method,but i think Not good enough.

AssemblyScript version

^0.27.0