test: End to End Test for Flutter Web Preloader

[tomarra]

Description

Right now we don't have a fully executing end to end test to confirm that the pre-loader is working as expected. Right now this is just a manual test. Overall this would have to be more of a browser based test, rather then just Flutter/Dart, as we need to confirm that the page actually loads correctly overall.

Requirements

• We have an end to end test to confirm that the pre-loader is loading the page correctly for the user
• The test runs in the CI when a PR is opened.
• All CI/CD checks are passing.
• There is no drop in the test coverage percentage.

Additional Context

No response

[marcossevilla]

closing as this brick is now part of Flame game template, see deprecation notice on README