[Feature request] Allow copy pasting text when creating Story post

[reginabally]

Is your feature request related to a problem? Please describe.
Currently, when we create a Story post in the app with text, the text will have to be entered through the keyboard. We're not able to paste the text copied from another source.

Describe the solution you'd like
Allow copy-pasting text when creating a Story post in the app

Additional context
Originally requested here: 4309425-zd-woothemes

[hypest]

👋 @aforcier ! Can you help triage this ticket? Thanks!

[aforcier]

Hi 👋 This seems to be an iOS only issue, and also related to the story creator (Kanvas) rather than Gutenberg mobile. Looks like we already have an open issue for it: tumblr/kanvas-ios#52.

So, I think we can close this one out as a duplicate. cc @bjtitus in case I've missed any nuance.