Improve Cast view color customization

This release improves overall consistency when customizing colors associated with a Cast button and its underlying views.

Improvements

• Added optional color parameter to the CastButton initializer. This color is applied to the button itself as well as to the underlying Cast device selection view. This mechanism supersedes usual foregroundStyle and tint color modifiers, which did not offer a reliable ways to customize this colors.

What's Changed

• Ensure proper color customization for CastButton by @waliid in #295

Full Changelog: 3.0.0...3.0.1