[Feature] elastic-package export pipelines

[nicpenning]

As an integration developer, it requires external tooling to use ingest pipelines in Kibana that have been developed and convert them to usable files in an integration (convert to YAML).

Similar to the Kibana export command where the data is exported in a usable format, I am purposing we can do that with elastic-package
 
#670 (comment)

It can be very easy for some to use Kibana to develop lengthy and worthwhile pipelines with a large sample set. So having the ability to run something like: elastic-package export pipelines and then be able to select the pipelines for export, this would save time having to convert them from JSON and ensure it's usable in the integration.