Add netcat-openbsd, patchelf, add note on container network

Dockerfile

 FROM ubuntu:oracular
 
-RUN apt update && apt install -y ca-certificates openssh-server python3-pip python3-dev xxd file qemu-user \
+RUN apt update && apt install -y ca-certificates openssh-server python3-pip python3-dev xxd file qemu-user netcat-openbsd patchelf \
                                 libssl-dev libffi-dev build-essential binutils-multiarch git gdb gdb-multiarch ltrace strace tmux wget curl && \
                                 apt clean && rm -rf /var/lib/apt/lists/* && touch /root/.hushlogin
 

README.md

@@ -183,6 +183,15 @@ Creates a 2 CPU, 4GB RAM VM with QEMU. Has Ubuntu and Docker preinstalled. While
 
 From here, you can choose to either use the Docker image or install the tools directly in your VM.
 
+### Reaching other containers
+
+If you're running the pwnenv container and want to reach local challenge containers from it that have ports exposed, connecting to localhost won't work.\
+You need to use the host IP address. To find it, run in your macOS terminal:
+
+```bash
+docker network inspect bridge -f '{{range .IPAM.Config}}{{.Gateway}}{{end}}'
+```
+
 ## Windows
 
 WSL2 is the easiest way to start.