feat(library/ac_match): add AC match design notes
feat(library/ac_match): add AC match design notes

fpvandoorn/lean,dselsam/lean,leanprover-community/lean,digama0/lean,digama0/lean,dselsam/lean,leanprover/lean,leanprover/lean,Kha/lean,Kha/lean,leanprover/lean,dselsam/lean,fpvandoorn/lean,digama0/lean,digama0/lean,leanprover-community/lean,dselsam/lean,Kha/lean,leodemoura/lean,fpvandoorn/lean,leodemoura/lean,Kha/lean,leanprover-community/lean,leodemoura/lean,Kha/lean,fpvandoorn/lean,fpvandoorn/lean,leanprover-community/lean,digama0/lean,leanprover-community/lean,leodemoura/lean,dselsam/lean,leanprover/lean,digama0/lean,leodemoura/lean,leanprover/lean,Kha/lean,leanprover/lean,fpvandoorn/lean,dselsam/lean,leanprover-community/lean,leodemoura/lean