[JS] Create Documentation

https://github.com/apache/arrow/tree/master/js currently only has a handful of examples but no API documentation.

**Reporter**: [Dominik Moritz](https://issues.apache.org/jira/browse/ARROW-2688) / @domoritz

_{**Note**: *This issue was originally created as [ARROW-2688](https://issues.apache.org/jira/browse/ARROW-2688). Please see the [migration documentation](https://github.com/apache/arrow/issues/14542) for further details.*}