Formalize problems from the Open Problem Garden

I suggest formalizing many problems from http://www.openproblemgarden.org/

It is one of the first sites that comes to my mind when I think about existing collections of open problems in mathematics.

No file, test, or specific problem is named. Start by reviewing the Open Problem Garden collection and narrowing it to one concrete conjecture, then compare it with existing formalized statements in the repository; done would require a clearly scoped problem and an agreed Lean formalization.

Written by the indexing model from the issue text.