`audio` feature is now no longer implied by the `3d`, `2d`, or `ui` features

Our default features used to be

• 2d
• 3d
• ui

where each of these features enabled the audio feature among others.

Since Cargo doesn't allow selectively disabling features, if you wished to disable bevy_audio, either because you don't need audio or because you use an alternative such as bevy_seedling, you had a problem with that. You needed to essentially enable all features enabled by the above except audio, leading to a big features soup. To avoid this, audio is now no longer enabled by the above features, but instead enabled by default, bumping our default features to:

• 2d
• 3d
• ui
• audio

Now what does this mean for you?

• If you used all default features before, nothing changes for you.
• If you want to opt out of using bevy_audio, it is now as simple as disabling default features, and manually opting into 3d, 2d, and/or ui.
• If you already opted into non-default features and want to continue using bevy_audio, you will now have to add the audio feature.