Share/Expose options and cleanup on exit

[stubbo]

I have started to use the share command and I prefer to use a different server to default.
This PR allows people to set some of the main options in .env so they don't have to add them on the end of the sail share command every time.

I also noticed that the expose container does not get removed when you stop sharing - every time you run the command a new container will be created, to fix this issue I added -rm which will remove the container upon exiting

Example:

Before

sail share --server-host=custom-server.com --domain=domain1.com --subdomain=subdomain --auth=amazing-auth-token

After

SHARE_DASHBOARD=4000
SHARE_SERVER_HOST=custom-server.com
SHARE_TOKEN=amazing-auth-token

sail share --domain=domain1.com --subdomain=subdomain