There is none and you should not look for one, if you have a legit project, people will join your group, no need to add them without their consent, it's a violation of telegram group regulations, the best way to invite people is to post your project here and invite them to join the group, on your post tell them what the group is all about and how they can benefit from joining, people will report your group if you violate their privacy, so just do the right thing.