This PR introduces four major features:

1. Background command execution - Ability to run long-running commands in background shells
2. ZSH support - Adds support for zsh shell in addition to bash
3. Prettier terminal output - Removed "wcgw ->" shell prompt. Instead users on zsh and bash would see their own default prompts.
4. Better handling of a new command while user is interacting with the same shell. It doesn't blindly enters the command and run.
5. Informative name of the background screens. wcgw vscode v0.4.0 extension now automatically attaches to the screen if it's opened in the same workspace.