feat(group_theory/subgroup/basic): add commute_of_normal_of_disjoint (#11751)
feat(group_theory/subgroup/basic): add commute_of_normal_of_disjoint (#11751)




Co-authored-by: Johan Commelin <759412786bc533369b22377bf83fb9056c5b25b2@commelin.net>

leanprover-community/mathlib,leanprover-community/mathlib