Quote arguments when executing in a shell (#118)

* Quote arguments when executing in a shell

Fixes #107

* Parse quotes in `tmux_arguments`

This makes it possible to encode spaces in arguments. Maybe the config
value should be an array instead?

* Print error causes

Co-authored-by: Thomas Schönauer <37108907+DottoDev@users.noreply.github.com>

src/steps/powershell.rs

@@ -79,6 +79,7 @@ impl Powershell {
         println!("Updating modules...");
         ctx.run_type()
             .execute(powershell)
+            // This probably doesn't need `shell_words::join`.
             .args(["-NoProfile", "-Command", &cmd.join(" ")])
             .check_run()
     }