Add new test data for sammyseq

[daisymut]

• [x] Check here that there isn't already a branch containing data that could be used
• [x] Fork the nf-core/test-datasets repository to your GitHub account
• [x] Create a new branch on your fork
• [x] Check your proposed test data follows the guidelines
• [x] Add your test dataset
  • [x] If you clone it locally use git clone <url> --branch <branch> --single-branch
• [x] Make a PR on a new branch with a relevant name
• [ ] Wait for the PR to be merged
• [ ] Use this newly created branch for your tests