AudioGenerator code prevents compiling if target isn't wasm.

[AdjectiveAllison]

src/audio.zig:17:18: error: root struct of file 'backend' has no member named 'AudioGenerator'
    peer: backend.AudioGenerator,
          ~~~~~~~^~~~~~~~~~~~~~~
src/backend.zig:1:1: note: struct declared here

The title is my current theory as to why it won't compile.
Related to this commit: b927197

Maybe defining a stub for non-wasm backends would be a good move?
Or some conditional to not even import audio on non initialized backends?

[AdjectiveAllison]

Maybe this is related to stage2 regressions ziglang/zig#12325?

@zenith391 mentions it here: #58

I'm getting something similar here when doing zig build serve with the capy-template build file:

src/components/TextArea.zig:13:19: error: root struct of file 'backend' has no member named 'TextArea'
    peer: ?backend.TextArea = null,

[zenith391]

Fixed by 9a4e757