chore(doc/changes): document new leanpkg features
chore(doc/changes): document new leanpkg features

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