adding numba to dependencies (#640)

Author: ipdemes

scripts/generate-conda-envs.py

@@ -111,6 +111,7 @@ def conda(self) -> Reqs:
             "scikit-build>=0.13.1",
             "setuptools>=60",
             "zlib",
+            "numba",
         )
         if self.compilers:
             pkgs += ("c-compiler", "cxx-compiler")