Add Concept Exercise for type checking.

[quintuple-mallard]

This PR adds the assembly-line exercise and type-checking concept to the JavaScript track.

A few notes/questions:

• I have noticed that some other tracks (C#, Go, and Ruby (and possibly more)) already have an exercise called Assembly Line, all on the numbers concept, but all slightly different. Does this matter?
• An error with nodejs that I haven't been able to fix has stopped me from running the format script. Configlet and the other node scripts have been working.
• The concept teaches Object.hasOwn rather than Object.prototype.hasOwnProperty, as it seems Object.hasOwn is the recommended over Object.prototype.hasOwnProperty, that is considered somewhat outdated.
• I have been coding via GitHub's online editor, often for only a few minutes, so there are quite a few very small commits.

[quintuple-mallard]

I've added you as an author, I feel that you have built a fair bit of the exercise.

[SleeplessByte]

I'll batch submit these. Then publish, have some people solve it, and then I'll add some more tests. Thanks for this. It's another great one @quintuple-mallard !

[SleeplessByte]

I'll fix main after this is merged.