ui: toast notification - implement component/module

[dsebastien]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Expected behavior

Separate module including component(s), styling and all the API related to this feature.
Mobile support.

What is the motivation / use case for changing the behavior?

See #104

[Dedepon]

I'm taking this (though I can't assign it to me...)

[christophercr]

Closed in #707