This change fixes tasks hanging due to rare cases of messages being lost between full Discord reconnections by placing a configurable timeout on the `ConnectionInfo` responses. This is a companion fix to [serenity#1255](https://github.com/serenity-rs/serenity/pull/1255). To make this doable, `Config`s are now used by all versions of `Songbird`/`Call`, and relevant functions are added to simplify setup with configuration. These are now non-exhaustive, correcting an earlier oversight. For future extensibility, this PR moves the return type of `join`/`join_gateway` into a custom future (no longer leaking flume's `RecvFut` type).
Additionally, this fixes the Makefile's feature sets for driver/gateway-only compilation.
This is a breaking change in:
* the return types of `join`/`join_gateway`
* moving `crate::driver::Config` -> `crate::Config`,
* `Config` and `JoinError` becoming `#[non_breaking]`.
This was tested via `cargo make ready`, and by testing `examples/serenity/voice_receive` with various timeout settings.
* 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.
