feat: Added tmux to lab container

lab/Dockerfile

@@ -7,6 +7,7 @@ RUN apk add --no-cache \
     jq \
     openssh \
     openssh-client \
+    tmux \
     sudo \
     ca-certificates \
     busybox-extras \
@@ -31,4 +32,4 @@ WORKDIR /home/dev
 
 RUN sh -c "$(wget -O- https://github.com/deluan/zsh-in-docker/releases/download/v1.2.1/zsh-in-docker.sh)"
 
-CMD [ "/bin/zsh" ]
+CMD [ "tmux" ]