You could include:
- a brief description of the plugin itself;
- instructions on normal installation for people that aren’t developers;
- how developers could use it;
- instructions on what to do if someone wants to contribute to the resource;
- and finally but not least, you could include a license section which tells you what you can do with the resource code.
I hope that all makes sense.
Edit: I made the reply look cleaner by removing the big paragraph and replacing it with bullet points. 😀