[Feature] Add emulation config examples to documentation

[DonaldTrumpAgent]

Unlike Playwright Nodejs that has a playwright.config.ts for presetting all the emulations.
The current documentation of Playwright Java has to use the JUnit test runners in order to configure different user agents.
However, the current example contains only the scenario where the test is only use one browser.
Would it be possible to add examples with different devices and browsers to the documentation ?