docs: add copyright notice (#972)

Close #972

README.md

@@ -18,6 +18,7 @@
  - [The bits and bytes (Python API)](#the-bits-and-bytes-python-api)
  - [Contributing](#contributing)
  - [Useful info](#useful-info)
+ - [Copyright notice](#copyright-notice)
 
 ## Overview
 
@@ -381,3 +382,14 @@ See [CONTRIBUTING](https://github.com/doronz88/pymobiledevice3/blob/master/CONTR
 ## Useful info
 
 Please see [misc](https://github.com/doronz88/pymobiledevice3/blob/master/misc)
+
+## Copyright notice
+
+This work is licensed under GPL 3.0, and as, credited to several major contributors:
+
+- Hector Martin "marcan" <[email protected]>
+- Mathieu Renard
+- doronz <[email protected]>
+- matan1008 <[email protected]>
+- Guy Salton
+- netanelc