Update index.md

Author: AlexKlo

docs/src/index.md

@@ -4,6 +4,12 @@ Wrapper for TDLib’s C JSON [interface](https://core.telegram.org/tdlib/docs/td
 
 ## Installation
 
+If you haven't installed our [local registry](https://github.com/bhftbootcamp/Green) yet, do that first:
+
+```
+] registry add https://github.com//Green.git
+```
+
 To install LibTDJSON, simply use the Julia package manager:
 
 ```julia