A first help for a beginner

Hello,

I am a beginner here in PostgreSQL development. My intention is to extend PostgreSQL and write plugins for it. Can you please direct me to where I can find the following general info ?

1. How to write a first plugin for pgAdmin ?
2. How to insert my plugin icon to the pgAdmin tree ? (like pgAgent does)
3. Where can I find a basic C++ plugin template ?

Thank you very much !!

Doron