feat(git): move to delta diff for diff in the terminal

Now when using git diff it will use delta for a much nicer diff format. This is
set for the show and log commands too.

See: https://github.com/dandavison/delta

site-modules/core/templates/git/gitconfig.erb

@@ -12,3 +12,22 @@
 
 [rerere]
   enabled = true
+
+[pager]
+  diff = delta --light
+  log = delta --light
+  reflog = delta --light
+  show = delta --light
+
+[interactive]
+  diffFilter = delta --light --color-only
+
+[delta]
+  line-numbers = true
+  navigate = true
+  hunk-header-style = raw
+  hunk-header-decoration-style = ul
+  file-modified-label = "modified:"
+  file-removed-label = "removed:"
+  file-added-label = "added:"
+  file-renamed-label = "renamed:"