fix(create): Default test script no longer errors

[fahslaj]

When running lerna create, the generated files will now include a test that is actually runnable via lerna run test.

Description

Motivation and Context

Before this change, running lerna run test on a newly created package would produce an error that told the user to "run tests from the root", which makes no sense. This change improves developer experience when using lerna create by leaving the user's workspace in a runnable state immediately after package creation.

How Has This Been Tested?

This has been tested manually, with and without --es-module, on a test lerna workspace. New unit tests have also been added as well as existing ones updated appropriately.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (change that has absolutely no effect on users)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.