Better document .g files and how to use custom germlines
vidjil-algo is able to handle different germlines, either from IMGT/GENE-DB, or for other sources.
options, the.g` file is very flexible.
However (Zhang, 2019) reports that "more effort should be made to manage customization".
We should ensure that this is properly documented. What is the syntax of the
.g file, and what are the recommended steps for anyone wishing to better use a custom germline ?