Reexport Fraction types from fraction.js instead of using custom one

[fchu]

This should fix #3317
FYI npm test passed but got issues with npm run test:types (prior to this PR that is), so an approver might want to double check

[josdejong]

Thanks Francois!

I was just thinking: maybe we should just remove exporting the type definition of Fraction, and let TypeScript pick the type defintions from the Fraction.js library itself. If we export Fraction from mathjs, as an end user, you can import Fraction from two different sources: mathjs or Fraction.js. That is a duplicate. What do you think?

[fchu]

I'm not an expert so I won't be able to give you the most informed answer.
I would think that if you remove the definition, the user will still have to import it from somewhere, which will either be their own direct import of fraction.js (which can be a different version), or have to find the exact version your package is depending on, which is an hassle. Maybe re-exporting it is just the user-friendly way to have access to the correct version of the type?

[josdejong]

Hm, yeah. If we change that we should be consistent and not export the type definition of Fraction nor BigNumber. Ok let's leave the export in then 👍.

[josdejong]

Published now in v14.0.1, thanks again.