Refactor/extract withGlobalDefaults

[zenflow]

Towards #1044

[zenflow]

With the deprecation warning I added last commit, the documentation site should be updated before publishing this (edit) updated in regards to Swal.mixin()

[limonte]

LGTM!

@zenflow you are building a strong foundation for the bright future of SweetAlert2 🌞

[zenflow]

@limonte 👍 Be sure not to publish before sweetalert2.github.io is updated in regards to Swal.mixin

[zenflow]

@limonte or users will get a deprecation notice saying to switch to using a method that's not documented yet

[limonte]

@zenflow roger!

[zenflow]

@limonte How are you liking Swal.mixin in practice?

[limonte]

How are you liking Swal.mixin in practice?

Can't live without it! :) Swal.mixin helped to eliminate tens of copy-pasted LoC with repetitive parameters.

[zenflow]

@limonte 👍 Be sure not to publish before sweetalert2.github.io is updated in regards to Swal.mixin
@limonte or users will get a deprecation notice saying to switch to using a method that's not documented yet

Eh, I guess we should get that documentation updated quickly since this is released in 7.19.0. I'll make a PR to the documentation site just adding the Swal.mixin method, and I think the rest of the edits (e.g. swal -> Swal can come in the new site.

[limonte]

@limonte +1 Be sure not to publish before sweetalert2.github.io is updated in regards to Swal.mixin
@limonte or users will get a deprecation notice saying to switch to using a method that's not documented yet

Oops. I forgot about this, apologies.

I'll make a PR to the documentation site just adding the Swal.mixin method, and I think the rest of the edits (e.g. swal -> Swal can come in the new site.

👍