Show a colorized diff for `diff3`-style conflict markers

**Is your feature request related to a problem? Please describe.**
When rebasing and solving merge conflicts I'm often facing something similar to the example below. I.e. multiple/many lines shared by two of the three hunks. It's hard to tell what has changed on the remote in this case and whether it's still safe to apply my own changes.

**Describe the solution you'd like**
The changes between top and middle hunk, and the changes between bottom and middle hunk should be a colorized diff:
- the removals / red lines should be in the middle hunk
- the additions and modifications / green lines should be in the top and bottom hunks
- bonus points for an additional word diff (similar to diff-so-fancy?)

**Describe alternatives you've considered**
Resolve the conflict in the editor of your choice, hopefully with highlighting there. However, that would defeat the purpose of solving merge conflicts quickly in lazygit directly in the hard-to-spot-but-simple-to-solve cases.

**Additional context**
Example:

```
<<<<<<< HEAD
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt
ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo
dolores et ea rebum. Stet clita kasd gubergren, no sae takimata sanctus est Lorem ipsum dolor sit
amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo
duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor
sit amet.
||||||| parent of xxxxxxxx (remove placeholder text)
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt
ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo
dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit
amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo
duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor
sit amet.
=======
>>>>>>> xxxxxxxx (remove placeholder text)
```

I'm sure you spotted the change in line 3 immediately ;). But for me, a colorized diff would really help in this case.

```diff
<<<<<<< HEAD
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt
ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo
+ dolores et ea rebum. Stet clita kasd gubergren, no sae takimata sanctus est Lorem ipsum dolor sit
amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo
duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor
sit amet.
||||||| parent of xxxxxxxx (remove placeholder text)
Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt
ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo duo
- dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit
amet. Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor
invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua. At vero eos et accusam et justo
duo dolores et ea rebum. Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor
sit amet.
=======
>>>>>>> xxxxxxxx (remove placeholder text)
```