[Enhancement] Outlined entry like in MD2

[Mikilll94]

Summary

In Material Design 2 there is an option to create an outlined entry like this:

However, in Xamarin it is not possible to create such an entry. And doing this with custom renderers is very hard.

API Changes

Many solutions are possible:

• add platform-specific on Android to enable outlined entries
• add border/outline prop to entry

Intended Use Case

As a developer, I want to easily create an entry with an outline.

[PureWeen]

duplicate #5005

[saiyamshah143]

@Mikilll94 You can refer this link. Custom Renderer is not too hard to implement.
https://stackoverflow.com/questions/59132739/outlined-textbox-in-xamarin-forms