feat: wrapper option

[HollyPony]

Add a simple wrapper option to encapsulate the template in a div.

I find it useful to manage dynamic modal based on routes (like my own use case), and not have to manage a third part element with appendElement option.

I'm open to discussions (since it's my first contact with you 🤗)

[dwmkerr]

Looks good! Seems like a useful option. It would be good to include a couple of tests, maybe one to assert that when wrapper is true, the element is wrapped, and another to test that if wrapperClass is provided, it is set on the element, WDYT?

[HollyPony]

Yeah that's a great idea, I've made a quick fix for my own purposes. And, finally, I have rewrite the whole service to integrate the component feature. It's still in progress work (you can check it here : https://github.com/HollyPony/angular-modal-service) .

I'll look for unit test and a document.createElement approach.