feature: document new CLI support for managing explicit bucket schemas (#2470)
* "explicit" schema-type for buckets
* `bucket-schema` to manage measurement schemas for buckets
* task-based overview of new bucket-schema feature in CLI for cloud.
* reference docs for bucket-schema and bucket schema-type.
* columns file examples.
other technical updates
* added shortcodes `get-leaf-text` and `get-assets-text`. Documented in CONTRIBUTING.md
Co-authored-by: Scott Anderson <sanderson@users.noreply.github.com>
Co-authored-by: kelseiv <47797004+kelseiv@users.noreply.github.com>
Co-authored-by: Kelly <kelly@influxdata.com>
Co-authored-by: null <kelseiv@users.noreply.github.com>
Jason Stirnaman