Add the --patch mode stuff to the README

Author: scottchiefbaker

README.md

@@ -22,6 +22,7 @@ Configure git to use `diff-so-fancy` for all diff output:
 
 ```shell
 git config --global core.pager "diff-so-fancy | less --tabs=4 -RFX"
+git config --global interactive.diffFilter "diff-so-fancy --patch"
 ```
 
 ### Improved colors for the highlighted bits