fix: path escaping

[Jakub-Vacek]

Description

This PR fixes two issues with path when using CLI on Windows: Invalid use of / in check was replaced with path.basename Windows \ are now escaped in assetsPath in .mjs file template

Motivation and Context

Types of changes

• [x] 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)

Checklist:

• [x] I have updated the documentation accordingly. For updating Oclif commands documentation use oclif-dev.
• [x] I have read the CONTRIBUTING document.
• [x] I haven't repeated the code. (DRY)
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.