Add demo of a DCS import

[mandolyte]

Create a demo showing how to import a DCS USFM text.

Simplest is to demo using a URL like this:
https://git.door43.org/unfoldingWord/en_ult/raw/branch/master/66-JUD.usfm

And allow the user to edit the code to change the URL to anything they wish. Unless there is something special about importing more than one, a demo showing how to import a single text like the above should suffice.

If the useImport takes a verbose option, be sure to provide metrics on the import process.
@klappy