Add sail run command

[rojtjo]

This PR adds the sail run command which allows us to run commands directly in the container.

I often create bash scripts in my projects in order to run a series of artisan command (or any command for that matter). In order to run these commands we currently have to do the following:

Open bash in the container:

$ sail bash

Then within the container:

$ ./some/path/to/a/command

With the sail run command we could just call it at once:

$ sail run some/path/to/a/command

PS: I considered expanding the sail bin command at first, but figured it would be safer to just add a new command instead. Please let me know if anyone feels different about this!