feat: add colorScheme parameter

[juaoose]

This PR allows the developers to programmatically change the color scheme of the map, the current behavior is that the map always follows the system (not Flutter's theme Brightness) appearance settings. There is still a bug regarding using the app's Brightness but I figured it can be worked on later, as that is the exact behavior atm.

This could be classified as a fix to #29, although that issue might involve more stuff than just the scheme.

Pre-launch Checklist

• I updated pubspec.yaml with an appropriate new version according to the [pub versioning philosophy].
• I updated CHANGELOG.md to add a description of the change.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making if a test is possible.
• All existing and new tests are passing.