feat: mageck count, test, & mle processes

[kelly-sovacool]

Changes

Implements processes for mageck count, test, and mle.

Issues

resolves #2

PR Checklist

(Strikethrough any points that are not applicable.)

• This comment contains a description of changes with justifications, with any relevant issues linked.
• [ ] Write unit tests for any new features, bug fixes, or other code changes. testing framework not yet implemented
• [ ] Update docs if there are any API changes. on backburner until first release
• If a new nextflow process is implemented:
  • docker container is set in conf/modules.config.
  • stub is defined.
• Update CHANGELOG.md with a short description of these changes and reference the PR number. Guidelines: https://keepachangelog.com/en/1.1.0/