Multiple diff tool support

**Is your feature request related to a problem? Please describe.**
In my git config I have multiple diff tools available depending on my exact need. In particular I have jsondiff/dyff installed which allow for much better understanding of how a json config file or jsonschema file has changed.

**Describe the solution you'd like**
Id like a way in the diff panel to switch to a different diff tool for the specific file. It would be ideal if this could be configured by file suffix so it would happen automatically, but a ui element to either cycle thru a set of diff tools or a ui element to select a diff tool would also be workable.

**Describe alternatives you've considered**
Just use plain git to do the diffs, but that requires me to either open another window or exit lazygit and then re-enter.