feat(algebra/module/localized_module): construction of module localisation (#14470)
feat(algebra/module/localized_module): construction of module localisation (#14470)

Give commutative ring $R$, multiplicative subset $S\subseteq R$ and an $R$-module $M$. We can localise $M$ by $S$ to be

$$
\frac ms = \frac n t \iff \exists (u \in S), u(sn - tm) = 0
$$

This pr makes this construction and proves that the localised module is an $R_S$ module.

Thanks @Vierkantor for substantial golfing.





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