Ploomber

* `ploomber scaffold` creates missing modules when adding functions ([332](https://github.com/ploomber/ploomber/issues/332), [fferegrino](https://github.com/fferegrino))
* `NotebookRunner` creates product's parent directories before running ([460](https://github.com/ploomber/ploomber/issues/460))

* Adds `ploomber nb` command for integration with VSCode, PyCharm, Spyder, etc.
* Adds methods for saving and removing injected cells to `NotebookSource`
* Adds methods for pairing and syncing to `NotebookSource`
* Fixes [448](https://github.com/ploomber/ploomber/issues/448): `SQLUpload` ignoring `io_handler`
* Fixes [447](https://github.com/ploomber/ploomber/issues/447): `pipeline.yaml` supports passing custom init parameters to `executor`
* Adds optional [anonymous user statistics](https://docs.ploomber.io/en/latest/community/user-stats.html)

* Fixes `{{root}}` expansion when path_to_here is different than the current working directory
* Better error message when initializing `MetaProduct` with non-products
* Adds refactoring section (`soorgeon`) to the user guide
* Adds shell scripts user guide
* `Commander` allows `jinja2.Environment` customization

* `GenericSource` supports extracting upstream

* Fixes an error that caused `copy.deepcopy` to fail on `SourceLoader`

* Adds `{{now}}` (current timestamp in ISO 8601 format) to default placeholders
* Adds `--output/-o` to `ploomber examples` to change output directory