doc(docs/overview): Update overview (#6772)
doc(docs/overview): Update overview (#6772)

Update the overview to mention Abel-Ruffini.



Co-authored-by: tb65536 <25c750517795e47f172dc8c552ed72c7de260bd4@users.noreply.github.com>

leanprover-community/mathlib,leanprover-community/mathlib