[command] viewport command

[kevinccbsg]

We need to create a similar experience of the cy.viewport command. We will have to change with and height of the body as we cannot simulate device interaction but it is the same as cypress does.

• create viewport command
• Add tests
• Update docs

[kevinccbsg]

We will not prio this, as I tested and we need to think about how to change viewport as height and other css properties rely on the user design and we will be affected by that. Maybe if we separate the test execution of react in a devtool we can think about it but for v1 this will not be included