Click and drag (single action) multi-line comments

Problem

The work being done as part of #218319 (closed) is a great next iteration for multi-line comments, however, it carries low discoverability and is not intuitive.

Proposal

In order to make the feature intuitive and discoverable, users should be able to click and drag inside a diff in order to insert a multi-line comment.

User should be able to click and drag the comment bubble to select a range (bonus if user can click and drag line number, however, because we link to line numbers that may be difficult)