docs: add GitHub-based install fallback (pip install git+https://...)

Author: Coding-Dev-Tools

README.md

@@ -14,6 +14,12 @@ Convert JSON files and datasets to SQL INSERT statements. Supports nested JSON,
 pip install json2sql
 ```
 
+Or install directly from GitHub:
+
+```bash
+pip install git+https://github.com/Coding-Dev-Tools/json2sql.git
+```
+
 ## Quick Start
 
 ```bash