Add support for creating module preloads for only the static dependencies

[dasa]

It currently seems to also create modulepreload's for the dynamic imports. I'd like these to only be loaded as needed.

[guybedford]

We could definitely add a --preload-static. Perhaps we could even make it the default and have --preload=dynamic for doing both static and dynamic preloading, where --preload=static is the default.

[dasa]

making it the default sounds good 😄