Document commit preview window bindings

Author: sodapopcan

README.md

@@ -110,7 +110,10 @@ Reload .vimrc and `:PlugInstall` to install plugins.
 - `:PlugStatus`
     - `L` - Load plugin
 - `:PlugDiff`
+    - `<CR>` or `o` - Preview the commit
     - `X` - Revert the update
+    - `<C-N>` / `<C-P>`  - Jump to next/previous commit
+    - `J` / `K` - Scroll the preview window without switching to it
 
 ### Example: A small [sensible](https://github.com/tpope/vim-sensible) Vim configuration