set neovim as default difftool and merge in ~/.gitconfig

[Salanoid]

I did something like that on my own configuration, maybe we have to update this file to update ~/.gitconfig with :

[difftool]
    prompt = true
[diff]
    tool = nvimdiff
[difftool "nvimdiff"]
    cmd = "nvim -d \"$LOCAL\" \"$REMOTE\""
[merge]
    tool = nvimdiff
[mergetool]
    prompt = true
[mergetool "nvimdiff"]
    cmd = "nvim -d \"$LOCAL\" \"$REMOTE\" \"$MERGED\" -c 'wincmd w' -c 'wincmd J'"

[Salanoid]

Regarding the .gitconfig, I came across an insightful article on how core Git developers configure their Git settings: How Git Core Devs Configure Git.
Perhaps we could leverage these ideas to develop a more sophisticated default .gitconfig.