* Add Makefile for common contributor tasks
Narrows down a few commands to automatically format when building, and neatly expose testing/benching.
Empty files added to describe contributor guidelines, overall architecture.
* First draft of contributor guidelines
* Simple architecture diagrams
* Add PNG variants of architecture diagrams
Swapping to these because not having Fira Sans installed on a viewing machine leads to terrible kerning.
* Architecture description.
* MD cross-refs.
This implements a proof-of-concept for an improved audio frontend. The largest change is the introduction of events and event handling: both by time elapsed and by track events, such as ending or looping. Following on from this, the library now includes a basic, event-driven track queue system (which people seem to ask for unusually often). A new sample, `examples/13_voice_events`, demonstrates both the `TrackQueue` system and some basic events via the `~queue` and `~play_fade` commands.
Locks are removed from around the control of `Audio` objects, which should allow the backend to be moved to a more granular futures-based backend solution in a cleaner way.
