allow `jest.config.mjs` and `jest.config.cjs` jest config files

[lukethacoder]

addresses https://github.com/salesforce/sfdx-lwc-jest/issues/313

allows the cli to recognize jest.config.mjs and jest.config.cjs as valid jest config files. The .(mjs|cjs) extensions are currently not supported.

I have explored adding support for .json and .ts but have chosen not to include.

• .json would require a bit more rework to allow importing on the JSON file.
• .ts would require adding types to the @lwc/jest-preset package (and potentially other TS based config)

[nolanlawson]

Thank you!!