Description

VCF suppliers like gnomad, provide VCF with the vcf.bgz extension (eg https://storage.googleapis.com/gcp-public-data--gnomad/release/4.1/vcf/exomes/gnomad.exomes.v4.1.sites.chr1.vcf.bgz ) . This PR adds vcf.bgz as a valid extension, defined as COMPRESSED_VCF_BGZ

Things to think about before submitting:

• Make sure your changes compile and new tests pass locally.
• Add new tests or update existing ones:
  • A bug fix should include a test that previously would have failed and passes now.
  • New features should come with new tests that exercise and validate the new functionality.
• Extended the README / documentation, if necessary
• Check your code style.
• Write a clear commit title and message
  • The commit message should describe what changed and is targeted at htsjdk developers
  • Breaking changes should be mentioned in the commit message.