Feature: Adds prop to preserve dialog in the dom

[franciscoemanuel]

Resolves #2346

• Adds prop MdKeepAlive for MdDialog component that allows the render to happen using v-show;
• Adds prop documentation for the Dialog page;
• Adds test scenarios on MdDialog component for use cases of this new prop;
• Creates a new abstract component (MdDialogRender) that implements different render methods (v-show or a v-if like) to MdDialog component;

The use for window.dispatchEvent(new Event('resize')) was an alternative for elements that uses resize observers such as MdTabs to be rendered correctly inside the dialog

[franciscoemanuel]

@marqbeniamin

[marqbeniamin]

Thank you, @franciscoemanuel, for your help. I will merge this to the dev branch