chore: Add GitHub Workflow

chore: Fix the Azure DevOps pipeline (#132)

- Downgrade the version of karma-sauce-launcher to match the isomorphic-git repo
- Use valid SauceLab configurations for Safari on macOS and iOS

Merge pull request #92 from isomorphic-git/fs-flush

add fs.flush() that saves superblock

Merge pull request #91 from isomorphic-git/low-level-backends

add to change low level backend

fix: allow changing 'backend' during 'init' (#65)

feat: add custom `backend` parameter (#63)

chore: sauce labs no longer has Safari 13.0

fix: default mode for symlinks should be 0o120000 not 0o666

Co-authored-by: Chris Thompson <chris@refinerylabs.io>

fix: add du to README (#46)

feat: add du method (#45)