refactor(README.md): clean up readme header
refactor(README.md): clean up readme header

digama0/lean,rlewis1988/lean,digama0/lean,leanprover-community/lean,johoelzl/lean,johoelzl/lean,Kha/lean,Kha/lean,Kha/lean,digama0/lean,leodemoura/lean,fpvandoorn/lean,johoelzl/lean,avigad/lean,Kha/lean,leanprover-community/lean,rlewis1988/lean,leodemoura/lean,leodemoura/lean,avigad/lean,digama0/lean,dselsam/lean,leanprover-community/lean,Kha/lean,leanprover/lean,dselsam/lean,leanprover-community/lean,dselsam/lean,digama0/lean,rlewis1988/lean,fpvandoorn/lean,leanprover/lean,leodemoura/lean,fpvandoorn/lean,fpvandoorn/lean,rlewis1988/lean,leodemoura/lean,johoelzl/lean,digama0/lean,avigad/lean,dselsam/lean,leanprover/lean,johoelzl/lean,dselsam/lean,fpvandoorn/lean,avigad/lean,leanprover/lean,avigad/lean,leanprover-community/lean,dselsam/lean,leanprover-community/lean,Kha/lean,johoelzl/lean,rlewis1988/lean,fpvandoorn/lean,rlewis1988/lean,leodemoura/lean,avigad/lean,leanprover/lean,leanprover/lean