Engine :: Windows Multi Media (WinMM) (#66) * add `WinMM` engine option to `README.md` * add testcase for WinMM * add `WinMM` to `Engine` Enum * add `_force_stop` attribute to reflect `stop` request from non-NavaThread to `WinMM` runner * it doesn't return `Process` * flag the `_force_stop` to make `WinMM` runner aware of `stop` request * implement `__play_winmm` function with the taste of `__play_winsound` to handle `WinMM` execution request * internal function to provide `play`, `stop` and `status` monitoring for WinMM execution * implement `__play_winmm_flags`, handle loop execution, sync mode, async mode (with polling) * shorten sound alias id similiar to git (last 7 characters of hash) * `CHANGELOG.md` updated * add \n before internal function definition * add more tests to increase coverage * call stop to increase coverage * modify testcases to increase coverage for `WinMM` * update function name * update docstring