Add diffnav bubble from Crush

[bashbunni]

it would be great to have the option for diffview as a bubble that users could use in their Bubble Tea programs and since it requires support in Crush, maybe it could be a good option as a bubble. This was also brought up in the Discord:

https://discord.com/channels/1032368467246075914/1404900884550516866/1408575885174378577
https://discord.com/channels/1032368467246075914/1404900884550516866/1408583271465619569

An existing project that has a diffview is https://github.com/dandavison/delta which has garnered a lot of interest

[ChausseBenjamin]

Not to mention that you also have soft-serve that navigates diffs when looking at commits. It would minimize code duplication on your end to have it as a bubble.