Added CI workflow, fixed data_vars bug, expanded tests, added API docs, and notebook runner.#117

GauravSRC wants to merge 3 commits intoioos:mainioos/xarray-subset-grid:mainfrom

GauravSRC:gsoc/ci-tests-docs-bugfixGauravSRC/xarray-subset-grid:gsoc/ci-tests-docs-bugfixCopy head branch name to clipboard