Create UI for File Upload, Part 2: Styling for "In Process" File Upload Pane

Purpose: To describe the UI changes when a user initiates drag and drop

Notes:

• This story extends work done in the UIDATIMP-33 story
• See wireframes and videos attached.
• If discrepancies between the text in the wireframes and text in the Jira story, use the text that is in the Jira story

Scenario:

• Given the Data Import landing page:
• When a User begins to drag one or more files to the 3rd (right-most) pane
• Then the UI for the drop area should change as per the attached wireframe and video
  • Background changes from light to black
  • Text changes from black to white
  • File name(s) & icon(s) appear in the drag and drop area
    Notes
• The component should allow for different actions to happen when the user releases the "drop" so that developers in other apps can choose to remain on the drag and drop area or advance the user to another page. Data Import will advance the User to another page, which will be detailed in another story
• For Data Import, if multiple files selected, the uploaded files will all need to be the same type (e.g. all MARC bibs, or all EDIFACT invoices). That check will happen on the next screen, once all files are uploaded.