Also added CH4 public WASM API

This allows better understanding of the ROMs and their purpose.

Also fixed small channel 3 issue

There's still no control over the channels themselves, but the basic interleaved buffer support is now coded.
There's also new support for buffer size definition in seconds.

Will allow performance update when not using audio.
Done for benchmark purposes.

Makes use of the new emukit audio code.

There are a series of hacks involved in making a constant stream of audio data to work OK with web audio.

Uses built package to print dependencies.

Normalized handling of ticks in SDL according to the Web version implementation.

Uses the `build.rs` file to generate compile time information about the build environment.
This information is exposed to the WASM environment through interface methods that are then used by the `Emulator` interface.

Theme stored in `localStorage`