Swap mainfields in build script

[ekwoka]

This reduces the build size of the AlpineJS module by ~20%

AlpineJS
Before: 112kb
After: 87kb

Focus Plugin:
Before: 32kb
After: 28kb

I've used a variation of this build myself on projects for a while now and have yet to see any actual issues in browser or with bundlers.

[calebporzio]

Interesting, here are my result before and after this change (there is no build size difference)
Before:

After:

Can you clarify what you're going for here and why it makes the bundle smaller? Of course I always love making the bundle smaller!

[ekwoka]

@calebporzio

Yes, that is because your build size report reports on the minified CDN size.

Not the esm module.

I should have clarified, but these sizes reported are the size of the output esm.js.

So those importing the project without using the CDN would be affected.

Naturally, the sizes shown are exaggerated from the esm not being minified, but it's still extra stuff.

I believe the cause is because esbuild is adding more code to allow it to import cjs packages (the main field) instead of using the available modules.

I don't know enough about what esbuild does, but diffing the two shows a lot of code for compatibility that doesn't exist in the CDN.

[calebporzio]

Ok, fair enough. Thanks for the explanation!