Make mantine packages play nice with nextjs optimizePackageImports.

[Abhirup-99]

This really reduces load times, but I am getting 404 on some packages. So I don't think this will be a lot of work, but just need to be looked into. Thanks for the library, really appreciate the effort.

[rtivital]

There is an example template with app router, it works correctly – https://github.com/mantinedev/next-app-template/blob/master/next.config.mjs#L13
pages router does not need this feature, tree shaking works correctly out of the box

[Abhirup-99]

@rtivital Just FYI, https://github.com/vercel/next.js/tree/canary/test/development/basic/barrel-optimization/fixture/pages
pages router does need the optimizePackageImports. I had some issues with CSS getting 404, but it went away on clearing the .next folder.

[Abhirup-99]

Pointer, getting GET /_next/static/chunks/pages/UnstyledButton.module.css.mjs.map 404
after adding the optimizePackageImports option.