Add supported extension list to the new publisher drag and drop

[mkolar]

Is your feature request related to a problem? Please describe.
Even though the new creators can specify what extensions they support, the user has no way of knowing this, other than blindly trying to drop various files into the drop zone in the Create new instance window.

Describe the solution you'd like
We should include all the supported extension of the give creator in the helper text. We should also let user know if the creator support multiple or single files.

[cuID:2hz0tnj]