[BA Studio] Multi-file support in .new

Motivation

• As a user, I would like to be able to view and edit multiple assets on the online editor;
• Currently, '.new' environment only supports editing a single file each time. The main goal of this iteration is to support multiple files in the same workspace(set of models) in .new environment, enabling use cases like DMN included models, sub-process, work item definitions, etc.

Goals

• Have the capability to upload multiple DMN models on the initial page of the online editor and add those models as 'included models' of my DMN;
• Be able to upload a folder from my local filesystem;
• Be able to import files from a zip file.

Expected behavior

• TBD

Testing

• What if folder/zip contains a not supported file format?
• What if folder/zip contains supported format but not a valid content?
• What if the folder/zip contains subfolders?

Documentation

• We should deliver a blog post covering this new feature;
• Update community docs accordingly