git-difftool: highlight git diff in command description (#5338)

pages/common/git-difftool.md

@@ -1,6 +1,7 @@
 # git difftool
 
-> Show file changes using external diff tools. Accepts the same options and arguments as Git diff.
+> Show file changes using external diff tools. Accepts the same options and arguments as `git diff`.
+> See also: `git diff`.
 > More information: <https://git-scm.com/docs/git-difftool>.
 
 - List available diff tools: