Strain: Add canonical data

[natanaelsirqueira]

Following the discussion that happened in this topic, this PR adds canonical data for the Strain exercise, using a list of test cases that have been implemented by the majority of the tracks.

Closes #588

[github-actions]

Hello. Thanks for opening a PR on Exercism. We are currently in a phase of our journey where we have paused community contributions to allow us to take a breather and redesign our community model. You can learn more in this blog post. As such, all issues and PRs in this repository are being automatically closed.

That doesn't mean we're not interested in your ideas, or that if you're stuck on something we don't want to help. The best place to discuss things is with our community on the Exercism Community Forum. You can use this link to copy this into a new topic there.

---

Note: If this PR has been pre-approved, please link back to this PR on the forum thread and a maintainer or staff member will reopen it.

[petertseng]

Please amend the commit message to include the string "closes https://github.com/exercism/problem-specifications/issues/588" or any equivalent string. Thank you.

This request is not affected by the fact that that issue is already closed. This commit should be marked as closing it anyway, even though it is already closed. That way all commits relevant to that issue remain accessible from that issue.

[ErikSchierboom]

Fantastic work! A couple of minor nits.

[ErikSchierboom]

Love this! Excellent PR

[ErikSchierboom]

CC @exercism/reviewers

[jiegillet]

This is great, thank you @natanaelsirqueira 🏅

[ErikSchierboom]

CC @exercism/reviewers