refactor: inappwebview example

[maxmitz]

Connection with issue(s)

There is no issue for this PR. This is a minor refactoring of the inappwebview example. I renamed the file from 'in_app_webiew_example.screendart' to 'in_app_webview_example.screendart' and did some small refactorings that have no implications on the behavior.

Screenshots or Videos

The project still runs

To Do

• double check the original issue to confirm it is fully satisfied
• add testing notes and screenshots in PR description to help guide reviewers
• request the "UX" team perform a design review (if/when applicable)