docs: write the README for v1

README.md

@@ -1,3 +1,37 @@
 # Elgato Light Controller
 
-Control an Elgato light by its IP address.
+Control one Elgato light by its IP address.
+
+## Installation
+
+This extension is not yet available at the official [Raycast store](https://www.raycast.com/store). However, you can still use it.
+
+#### Requirements
+
+- An Elgato brand key light or ring light
+- The light has a dedicated IP address
+- node / npm / git
+
+#### Process
+
+Clone this git repository and **cd** into the folder.
+
+```shell
+git clone https://github.com/wassimk/raycast-elgato-light.git
+cd raycast-elgato-light
+```
+
+Run npm install and start the extension in development mode
+
+```shell
+npm install && npm run dev
+```
+
+The extension will launch and be installed locally. Even if you quit `npm run dev` with **CTRL-C**, it will remain installed.
+
+## Acknowledgments
+
+This extension is a wrapper around the CLI tool called [elgato-light](https://github.com/wassimk/elgato-light), which lets you control a light with the command line. 
+
+Also, thanks to Raycast for making such a fantastic and easy tool to develop with!
+