Add command to start project and go to shell

In every development session, I use devenv up -d && devenv shell to run the project and access required tools. When I'm done, I have to exit twice: 1) exit the shell and 2) run devenv processes down.

This process could be streamlined into a single command that:

• starts the project
• drops the user into a shell with project tools
• on exit, stops processes and exits the shell