Use `grabix` to detect compression mode of FASTA input.

[subwaystation]

Is your feature request related to a problem? Please describe

If I enter give nf-core/pangenome a GZIP compressed FASTA as input, WFMASH will complain.

Describe the solution you'd like

Use grabix in order to find out if the input file was GZIP or BGZIP compressed. If it was GZIP compressed, uncompress it, compress it with BGZIP, index it, then run the pipeline.