Change bwt2_index input to take input tar/tar.gz file rather than path + base name

[IttaiEres]

Description of feature

Could the bwt2_index input parameter be structured such that an input tar/tar.gz file can also be taken, rather than a path with a base name? I believe nf-core Cut & Run's prepare_genome.nf implementation does this already. I ask because in some compute environments, the lack of an existing file that has the base name of the indices can cause an issue.

Thank you!