[Feature] Demo Pane viewport and theme support

[akhileshThapliyal]

Description

Ability to render angular components in different viewports in the demo pane. There are instances when a component needs to be rendered in different viewport to validate the design requirements. The theme support is also valuable, as it allows us to visualize the component under different themes as per the design specifications.

Proposed solution

There should be a way in the ng-docs for us to be able to view the components in different viewport. The viewports should also be able to be configured where we can configure the device resolution. This is the same feature of a storybook, which allows for configuration of different device sizes.

https://storybook.js.org/docs/essentials/viewport
https://storybook.js.org/docs/essentials/toolbars-and-globals

Alternatives considered

Storybook provides these features as part of its offerings.