feat(library/init/logic): allow exists.intro to be used in pattern matching
feat(library/init/logic): allow exists.intro to be used in pattern matching

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