Allow image pasting in rich text mode in RTE (#11049)
* add comments to rough first solution
* allow eventRelation prop to pass to both composers
* use eventRelation in image paste
* add image pasting to rich text mode of rich text editor
* extract error handling to function
* type the error handler
* add tests
* make behaviour mimic SendMessage
* add sad path tests
* refactor to use catch throughout
* update comments
* tidy up tests
* add special case and change function signature
* add comment
* bump rte to 2.2.2
