Created Mypy stub for timeit module.
Created Mypy stub for timeit module.

* Refer to instructions https://github.com/python/mypy/wiki/Creating-Stubs-For-Python-Modules
* Created stubs directory: mkdir stubs
* Exported the stubs path: `export MYPYPATH=/Users/<my_username>/code/aind-projects/clones/nd889/2_isolation/stubs`
* Found relevant stubs at the [Typeshed repo](https://github.com/python/typeshed). Copy and pasted the timeit.pyi stub posted on the typeshed GitHub repo [here](https://github.com/python/typeshed/commit/9e39eb636867262584eaf71a31b639afba76f279) into the stubs directory to remove Mypy error `isolation/isolation.py:11: error: No library stub file for standard library module 'timeit'`

madhavajay/nd889,madhavajay/nd889,madhavajay/nd889,madhavajay/nd889