Add example of app configuration to documentation

[miloskroulik]

On the page https://wingsuit-designsystem.github.io/configurations/details/ I can see the description of app configuration. However, the concrete example is missing (similar to what's available for designSystem configuration). There's also no example in the default wingsuit.config.js file. Would it be possible to add it?

For example, it's not clear what's expected under cssMode key.

[christianwiedemann]

You are right. Thanks for reporting.