mmap is not implemented

Feature

Currently, I'm working on adding test_os.py test file. Then I met this error.

Traceback (most recent call last):
  File "Lib/test/test_os.py", line 15, in <module>
    import mmap
ModuleNotFoundError: No module named 'mmap'

mmap module in CPython is not implemented on RustPython.

Python Documentation

https://docs.python.org/3/library/mmap.html