Enhancement: Copy Block reference to annotation from Annotation view

[adam-wood]

This is similar to #76

It would be helpful to be able to quickly copy a block reference for pasting to another note directly from the Annotate view. This would be easier to then paste these into other notes.

Currently, we need to create a block reference and then search through the annotations which can be hard to get the right one.

This could possibly be accomplished by tying this function to the original share button in Hypothesis:

If there is interest in taking this further, I can write a more descriptive use case.