Document the proper way to set the shell type

[hammerandtongs]

Despite the amount of good documentation for this package I still had basic trouble even getting it to work.

(use-package shell-pop :ensure t :custom (shell-pop-shell-type '("eshell" "eshell" (lambda () (eshell)))) (shell-pop-full-span t))

Was where I ended up.

The fundamental issue was that shell-pop-shell-type doesn't take "eshell" or 'eshell but instead that full chunk of code but that didn't seem clear to me from reading the documentation.

I would ask that you add the eshell line in its entirety (and the other shells) explicitly in the documentation.

I also think adding the use-package boilerplate would be a nice thing to add these days. A small note that using ":custom" is important since shell-pop uses customize.