Update README.md

Author: nschlimm

EasyKey.git/README.md

@@ -11,5 +11,5 @@ To get startet with the full functionality:
 1. Install `git` on the command line. (MACOS: `brew install git`)
 2. Install `git-extras` on the command line. (MACOS: `brew install git-extras`)
 3. Install `git-filter-repo` on the command line (MACOS: `brew install git-filter-repo`)
-5. You need to define a Diff tool, you can do that with EasyKey.git in 'Setting up repositories' > 'Define merge/diff tool'.
+5. You need to define a Diff tool, you can do that with EasyKey.git in 'Setting up repositories' > 'Define merge/diff tool'. Use 'vimdiff' for instance.
 6. Start the menu with `bash git.sh` or with `bash path/to/git.sh`