Allows users to export existing cards for Google docs

[c-okelly]

The user should be able to export existing cards via a text format.

They can then paste this into the Google doc and the add-on should sync the new cards. User's who exported the cards should not have their own cards moved for the first version

[kimo-supremo]

bringing this back! i hope work is done on this as this has great potential. I would like to be able to export decks