Allow .bgz/.bgz.tbi files to be read in TabixParser

Created by: ima23

Description

Some resources use .bgz as ending for a BGZF-compressed vcf files (example gnomAD). Currently TabixParser allows only .gz files to be read.

Use case

The current changes will allow users to use .vcf.bgz files for VEP custom annotations.

Benefits

TabixParser will be able to process .bgz files and allow extended VEP custom annotations.

Possible Drawbacks

If applicable, describe any possible undesirable consequence of the changes.

Testing

Have you added/modified unit tests to test the changes?

Yes.

If so, do the tests pass/fail?

Tests pass.

Have you run the entire test suite and no regression was detected?

Yes, tests passed.