How did ESM integeration go?

[Andrea Giammarchi <andrea giammarchi gmail com>]

Dear GJS developers,

  I am looking forward to see https://gitlab.gnome.org/GNOME/gjs/-/issues/328 finalized but meanwhile, I'd like to ask any of you if you could summarize what was the biggest pain point in implementing ESM and if you ever had any issue in shipping this using `.js` file without worrying about old vs new syntax.

Thanks in advance for any sort of explanation, I am trying to help bringing the `-m` flag (under a different name, apparently) to node as well, and it'd be great if you could share any specific gotcha you had there, if any at all.

Best Regards