feat(field_theory/abel_ruffini): solvable by radicals implies solvable Galois group (#6631)
feat(field_theory/abel_ruffini): solvable by radicals implies solvable Galois group (#6631)

Proves the theoretical part of insolvability of the quintic. We still need to exhibit a specific polynomial with non-solvable Galois group



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

leanprover-community/mathlib,leanprover-community/mathlib