feature(init): adds extensions detection to one shot configs

[sverweij]

Description

• adds detection of extensions in the current project to the --init command

Currently limited to the (likely not widely used) 'one shot configs' so we can gain experience before baking it into the regular set up code.
Only used to reduce the array of extensions to pass to enhanced-resolve

Also (🏕️ camping site rule):

• corrects dependency-cruiser's own config to also check for .mjs extensions
• corrects user input code to be typed correctly
• moves some utility functions from src/extract/utl to src/utl as they're now use from both src/extract and src/cli
• adds a file that gets temporarily created during testing to .gitignore

Motivation and Context

It's typically faster to pass less extensions to enhanced resolve than everything dependency-cruiser supports - each extra extension potentially leads to one extra lookup on the file system per dependency. Also the resolver traverses the array in order, so putting the most likely extension to occur at the front will also make it find things faster.

How Has This Been Tested?

• green ci
• additional unit test(s)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• Documentation only change
• Refactor (non-breaking change which fixes an issue without changing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist

• 📖

  • My change doesn't require a documentation update, or ...
  • it does and I have updated it

• ⚖️

  • The contribution will be subject to The MIT license, and I'm OK with that.
  • The contribution is my own original work.
  • I am ok with the stuff in CONTRIBUTING.md.