feat(library/init/meta/tactic): add to_string instance
feat(library/init/meta/tactic): add to_string instance

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