[Feature request] Alert component

[guastallaigor]

What problem does this feature solve?

This feature request is to add a new alert component kind of like this.

What is your proposed solution?

An alert component <dm-alert> with this props:

Prop	Type	Default	Description
active	Boolean	false	If true then the component is visible.
title	String	null	Set the alert title.
closable	Boolean	false	If true then the user can close the alert left clicking the close material icon.
icon	String	null	Add a left icon (see material icons).
icon-size	String	"default"	Set the icon size."mini" | "small" | "default" | "medium" | "large"
color	String	black	Set the alert color."black" | "blue" | "green" | "orange" | "red" | "white"

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Note: I already have the code and I will make a PR to see if you approve it.