Green's Open Problems #100

### What is the conjecture
https://people.maths.ox.ac.uk/greenbj/papers/open-problems.pdf#problem.100

Is every group well-approximated by finite groups?

### [AMS categories](https://github.com/google-deepmind/formal-conjectures/labels?q=ams-)

* ams-20

### Choose either option
- [ ] I plan on adding this conjecture to the repository
- [x] This issue is up for grabs: I would like to see this conjecture added by somebody else

Read problem 100 in the linked Green PDF first to determine the precise conjecture and its definitions. Then inspect the repository's existing formalized conjectures for the expected statement structure; done means adding this conjecture in the repository's established Lean format.

Written by the indexing model from the issue text.