Add support for "isMobile" argument for "browsingContext.setViewport" command

[whimboo]

Both Puppeteer and Playwright support an isMobile boolean argument for the setViewport command, which is currently missing in WebDriver BiDi. We should add support for this parameter with the following behavior:

• Default Behavior: By default isMobile is set to false, meaning the device is not treated as a mobile device and touch events are not enabled.

• Mobile Mode: When isMobile is set to true, the browser will behave as if it's running on a mobile device. This includes rendering the website in mobile mode by taking the meta viewport tag and CSS media queries into account. Additionally, touch events are enabled, allowing mobile interactions like swiping and tapping.

Question: We currently support touch events in input.performActions by default. How should these behave when mobile mode is disabled? Should we consider disallowing their use in this case?

[whimboo]

Question: We currently support touch events in input.performActions by default. How should these behave when mobile mode is disabled? Should we consider disallowing their use in this case?

There is actually a hasTouch argument as well that we do not cover yet and I filed #773 for.