This MR adds the ability to leave multi-line comments and suggested changes to an MR. The features are only supported for `diffview` because we plan to deprecate `delta` as a reviewer soon.
This plugin previously only supported the Delta reviewer. Thanks to work
from @mrparalon it now supports Diffview also. This MR adjusts the
requirements to account for this, and the README.
It also addresses a small bug in the original implementation regarding
an async file opening action, and applies formatting to the diffview
file consistent with the rest of the project
