ballot .3 release

update pre-release build

fix typo

pre-release versioning

trial use

update SeqLoc documentation to discuss sequence attribute

Merge pull request #418 from ga4gh/main

v1.3 release candidate

Merge branch 'issue-361'

update schema to match paper. second pass at #324.

Closes #282: Merge pull request #283 from ga4gh/issue-282

#282: VariationSet in VRS Python