Update bin/add-exercise

[keiravillekode]

Updated from generic-track

We extend the script to sort exercises by (difficulty, slug)

[kotp]

The title and topic of this seems to be "Update bin/add-exercise" but it has more than only that.

The restructuring of the order of the exercises is a completely different topic.

These should be two different pull requests, right?

If this had only the adjustment of the difficulties, I would have approved it and we would be done with that. But because it is attached to this topic, it is going to be more convoluted.

It is a good thing that the commits are atomic, though, so this is easily remedied.

[keiravillekode]

I added sorting to bin/add-exercise, so then I also sort config.json But then some problematic difficulty estimates become obvious (anagram should not be 1).

Now extracted the difficulty adjustment into #453

From there, the config.json in this PR can be recreated using

filter='.exercises.practice = (.exercises.practice | sort_by(.difficulty, .slug))'
jq "${filter}" config.json > config.sorted && mv config.sorted config.json

[kotp]

So this patch should likely only involve commit d461540 right?

Effectively, the re-evaluation of difficulty is not here. However, the original description of this pull request should be updated to describe the PR as it currently is.