feat(linear_algebra/finite_dimensional): add dim_sup_add_dim_inf_eq (#3304)
feat(linear_algebra/finite_dimensional): add dim_sup_add_dim_inf_eq (#3304)

Adding a finite-dimensional version of dim(W+X)+dim(W \cap X)=dim(W)+dim(X)





leanprover-community/mathlib,leanprover-community/mathlib