Improve approach to use custom fonts libraries or just local fonts.

[jr-rootstrap]

On last project we use this library to put custom google fonts: https://pub.dev/packages/google_fonts

But we face an issue when this ones was tried to get customized in the theme, and used into the UI. Basically when we try to put as a bold, italic, etc.

The idea of this issue is investigate why this is happening and maybe propose another approach to have custom fonts like this in the project.

Maybe the idea is use the fonts as a local asset:

https://docs.flutter.dev/cookbook/design/fonts