:boom: add meta to freebayes/multi input channels

PR checklist

Closes #15

[ ] 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 module conventions in the contribution docs
[ ] If necessary, include test data in your PR.
[ ] Remove all TODO statements.
[ ] Emit the versions.yml file.
[ ] Follow the naming conventions.
[ ] Follow the parameters requirements.
[ ] Follow the input/output options guidelines.
[ ] Add a resource label
[ ] Use BioConda and BioContainers if possible to fulfil software requirements.
Ensure that the test works with either Docker / Singularity. Conda CI tests can be quite flaky:
- [ ] PROFILE=docker pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware
- [x] PROFILE=singularity pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware
- [ ] PROFILE=conda pytest --tag <MODULE> --symlink --keep-workflow-wd --git-aware