Add practice exercise line-up

[FraSanga]

https://forum.exercism.org/t/adding-exercises-to-elixir-track/33067/2

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  • 🏆 Does this PR need to receive a label with a reputation modifier (x:size/{tiny,small,medium,large,massive})? (A medium reputation amount is awarded by default, see docs)

• Any exercise changed

  • 👤 Does the author of the PR need to be added as an author or contributor in <exercise>/.meta/config.json (see docs)?
  • 🔬 Do the analyzer and the analyzer comments exist for this exercise? Do they need to be changed?
  • 📜 Does the design file (<exercise>/.meta/design.md) need to be updated to document new implementation decisions?

• Practice exercise changed

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[Copilot]

Pull request overview

Adds the new Elixir practice exercise “Line-up”, introducing learners to generating English ordinal suffixes and interpolating them into a fixed sentence format, and registers the exercise in the track configuration.

Changes:

• Add the new line-up exercise skeleton (stub module, tests, Mix project files, formatter/gitignore).
• Add exercise authoring metadata (.meta/config.json, example solution, generated tests.toml) plus learner-facing docs (.docs/*).
• Register the exercise in the track-level config.json.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
exercises/practice/line-up/test/test_helper.exs	Standard ExUnit setup for pending tests.
exercises/practice/line-up/test/line_up_test.exs	Adds test suite covering ordinal suffix rules.
exercises/practice/line-up/mix.exs	Adds Mix project definition for the exercise.
exercises/practice/line-up/lib/line_up.ex	Adds the student-facing stub API (LineUp.format/2).
exercises/practice/line-up/.meta/tests.toml	Adds configlet-generated test UUID mapping.
exercises/practice/line-up/.meta/example.ex	Adds reference implementation for ordinal suffix formatting.
exercises/practice/line-up/.meta/config.json	Adds exercise metadata (files, blurb, attribution).
exercises/practice/line-up/.gitignore	Adds standard Mix build/deps ignores.
exercises/practice/line-up/.formatter.exs	Adds formatter configuration for the exercise.
exercises/practice/line-up/.docs/introduction.md	Adds narrative introduction for the exercise.
exercises/practice/line-up/.docs/instructions.md	Adds problem statement and suffix rules.
config.json	Registers line-up in the Elixir track exercise list.

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[jiegillet]

This looks great, nice job!

I left some small comments, let me know what you think.

[jiegillet]

I think the official name doesn't have a dash: https://github.com/exercism/problem-specifications/blob/main/exercises/line-up/metadata.toml

(BTW, this is a neat little contribution someone could make to the generator in a separate PR: read the name from that file instead of using "TODO")

[FraSanga]

(BTW, this is a neat little contribution someone could make to the generator in a separate PR: read the name from that file instead of using "TODO")

Great idea. As soon as I have time, I'll do the PR for that too.
In the meantime, I'll create an issue so it stays marked and we can remember it. (#1621)

EDIT: precheck keeps failing, but I don't see any problems.

[jiegillet]

The precheck was failing because the test file wasn't formatted correctly after your changes. I pushed a commit to fix it.

[jiegillet]

Looks great, thank you very much :)