Exit on ctrl+c

[popzxc]

cargo-workspaces sets the ctrl+c handler that doesn't terminate the program. When working with large workspaces, I find myself having to kill it with sigterm instead of sigint. This PR fixes it.

Before:

$ cargo ws plan --skip-published
error: config value `http.cainfo` is not set
^C^C^C^C^C^C^C^C
[1]    8534 terminated  cargo ws plan --skip-published

After:

$ cargo ws plan --skip-published
error: config value `http.cainfo` is not set
^C%