Label spans - extending tokens

[flaviuGC]

As a user, I want to be able to create a label for a span of tokens by

clicking and dragging across the tokens, which will highlight the tokens

The updated span should be reflected in the parsed data. Using the Extended UI example on TAG's homepage, if I were to add a new span on the token by, I could add the label prep. Then I could look at the Parsed data object below the extended example and see that label prep in Object > tokens > 9 > registeredLabels > default > val: "prep".