docs: Added Source

Author: Mr-Sunglasses

src/paste/templates/index.html

@@ -5,6 +5,8 @@
 
       A simple pastebin powered by <a href="https://fastapi.tiangolo.com/">FastAPI</a>.
 
+      Paste is Fully Free and Open-Source <a href="https://github.com/FOSS-Community/paste.py">Source Code</a>.
+
       Simple API. CLI. Web form.
 
       Web Form: <a href="https://paste.fosscu.org/web" alt="paste.py web interface">https://paste.fosscu.org/web</a>