Add a bgzip module for dbsnp files

[nschcolnicov]

Description of feature

I recently came across a new issue that I wasn't getting in the version previous to this PR: #140.
This process is complaining about my dbsnp file not being BGZF:
NFCORE_RNAVAR:PREPARE_GENOME:TABIX_DBSNP

Easiest way would be to just bgzip the file and use the new file as input, but I have limited capabilities in my current working environment, so it is more efficient for me to have it being done within the pipeline execution.

The scope of this ticket is to add this module inside the prepare_genome subworkflow