Readme updates

README.md

@@ -2,6 +2,11 @@
 
 Inspired by https://github.com/fdw/rofimoji but written as rofi-script instead of starting a separate rofi.
 
+## Prerequisites
+
+ * An emoji capable font, for example [Noto Emoji](https://www.google.com/get/noto/#emoji-zsye) or [Noto Color Emoji](https://www.google.com/get/noto/#emoji-zsye-color).
+ * xsel to copy the selection to the clipboard. You should find it in your package manager.
+
 ## Usage Example
 ```sh
 rofi -modi 'run,drun,emoji:/path/to/rofimoji/rofimoji.sh' -show emoji