Minigraph-0.21 (r606)

Notable changes:

• New feature: added mgutils-es6.js for converting merged BED to VCF. This
  replaces the older BED-to-VCF converter. This script requires k8 v1.0.

• New feature: output a new ds:Z tag. ds is similar to cs but it
  additionally indicates microhomology around INDELs.

• New experimental feature: added gafcall.js for calling structural
  variants. This script will be moved a separate repo in future.

(21 April 2024, r606)