Copy Commit Message Functionality

[Xaypanya]

First, thank you for the excellent work on Git Graph! It’s an essential tool for many developers, and its user interface is a joy to work with.

I would like to request a new feature that allows users to easily copy the commit message of a selected commit directly from the Git Graph interface. This feature would streamline workflows, especially for users who frequently reference or reuse commit messages in their development process.