Missing package mock for cross-platform development

[sjpark608]

Please package mock line in unittest files which imports peripheral package.

The following import and mock is required for vscode to discover the unittest in Windows environment

import sys
from unittest import mock
sys.modules["periphery"] = mock.MagicMock()

https://github.com/osensa/edgepi-python-sdk/blob/ab02437422b6341932cdb9b778190f8b86c3e834/src/test_edgepi/unit_tests/test_adc/test_adc_state.py#L1-L18