added command to source gdbinit.py

you need to source gdbinit.py for it to take effect

README.md

@@ -36,6 +36,7 @@ Installation is straightforward.  Pwndbg is best supported on Ubuntu 18.04 with
 git clone https://github.com/pwndbg/pwndbg
 cd pwndbg
 ./setup.sh
+echo "source $(pwd)/gdbinit.py" >> ~/.gdbinit
 ```
 
 Other Linux distributions are also supported via `setup.sh`, including:
@@ -62,4 +63,4 @@ Want to help with development? Read [CONTRIBUTING](.github/CONTRIBUTING.md) or [
 
 ## Contact
 If you have any questions not worthy of a [bug report](https://github.com/pwndbg/pwndbg/issues), feel free to ping
-anybody on [Discord](https://discord.gg/x47DssnGwm) and ask away.
+anybody on [Discord](https://discord.gg/x47DssnGwm) and ask away.