Add a config and samplesheet using nf-core/sarek test datasets

[DonFreed]

Add a test profile using the small Sarek test dataset at https://github.com/nf-core/test-datasets/tree/sarek.

Addresses #2.

PR checklist

• [ ] This comment contains a description of changes (with reason).
• [ ] If you've fixed a bug or added code that should be tested, add tests!
  • [ ] If you've added a new tool - have you followed the pipeline conventions in the contribution docs
  • [ ] If necessary, also make a PR on the nf-core/sentieon branch on the nf-core/test-datasets repository.
• [ ] Make sure your code lints (nf-core lint).
• [ ] Ensure the test suite passes (nextflow run . -profile test,docker).
• [ ] Usage Documentation in docs/usage.md is updated.
• [ ] Output Documentation in docs/output.md is updated.
• [ ] CHANGELOG.md is updated.
• [ ] README.md is updated (including new tool citations and authors/contributors).

[drpatelh]

Thanks! Be a good idea to update the Github Actions to run this test too or maybe we can replace the existing test 🤔