Minibrowser: Add to mobile examples

We should consider making Qt WebView Examples - Minibrowser a good mobile example that is also shown in the category.

Mobile platforms are currently the pirmary use case of Qt WebView, as shipping Qt WebEngine on Android and iOS is not feasible or supported. I'd like to therefore add the only example for the module, Minibrowser, to the mobile category.

Anyhow, trying out the example on e.g. Android also shows some shortcomings that let it look alien:

• The left, right, reload buttons do not properly render . THey should arguably be made part of the burger menu.
• Entering a new URL in the text edit is not enough. One has to finally click the 'go'button. For Android at least, I expect that finishing the editing in the virtual keyboard is enough.
• Burger menu look and location is non-native

If we could fix these issues, I think Qt WebView would be a good example also for use of Qt on mobile.