Update README (missing link to fish key bindings file)

README.md

@@ -237,7 +237,8 @@ If you use vi mode on bash, you need to add `set -o vi` *before* `source
 ~/.fzf.bash` in your .bashrc, so that it correctly sets up key bindings for vi
 mode.
 
-The source code can be found in `~/.fzf.bash` and in `~/.fzf.zsh`.
+The source code can be found in `~/.fzf.bash`, `~/.fzf.zsh`, and
+`~/.config/fish/functions/fzf_key_bindings.fish`.
 
 Auto-completion
 ---------------