[GitHubActions or travis ci] Add test that validates oem as datapackage compatible

[jh-RLI]

I think it would be good if a datapackage validation is added as CI rule to the repository. The OpenEnergyMetadata repo is practically the datapackage.json and therefore should be always compatible to datapackage. This guide explains how to get started with frictionless datapackage.

Also add datapackage dependency to requirements.

[jh-RLI]

FYI @henhuy

[henhuy]

I'm actually implementing this in modex repo as possbility to upload datapackages to the OEP.
Still in progress. Will share link once it's working...

[jh-RLI]

the validation is already successfully used when uploading with the oedatamodel_api to the OEP. We could adopt the functionality to validate the oemeta data automatically in the first step. (By extending the CI pipeline travis/gthub actions).

From the findings with the oedatamodel_api, the schema must first be adapted so that all fields of the oemetadata strign can be successfully validated. Currently only the fields of the resources are tested. This also means that the oemetadata string is not conform with the frictionless datapackage format respectively with the required datapackage.json file.