feat(slide-toggle): Customized slide toggle for theming featuring light / dark mode icon

[monacodelisa]

Feature Description

The feature I am suggesting is to add and additional slide-toggle button option
that is already customized for theme switching control.

• having integrated theme appropriate icons within the mdc-switch__icons
• to replace the two SVGs that are currently within

I implemented it in one of my projects using vanilla JS and thought that it might be nice to have it as and option available

• as a ready component within Angular Material Examples page.

here is a screenshot from my app:

Light Mode

Dark Mode

I have now implemented it on a second app too

• view live

Use Case

The slide-toggle component is often used as theme switcher,
so I think that it would be very nice to have it ready and available.

The new design makes it easy to implement.