diff tool updates

Continued on the diff tool.

Screenshot of the diffing tool. There are two inputs at the top, labeled "Original" and "Changed". Then a button labeled diff. Underneath the diff between the original and diffed inputs. Once mixed, and underneath split into original, with the removals, and next to it changed, with the additions in the changed input.

It's been complicated making things work nicer, and the diffing libraries seem more focused on diffing for version control systems/unit tests, where the focus is more that a line changed. Rather than what gives a nice visual diff.

I also struggled a lot, with detecting added/removed lines.

For now I view this still as work in progress. Let's see when I feel up to working on it again :D