Merge #343

343: Add scapegoat to no-std crates r=eldruin a=tnballo

Add [`scapegoat`](https://crates.io/crates/scapegoat) crate to the list.

It's a mostly "drop-in" replacement for the standard library's `BTreeMap` and `BTreeSet`. Subset of the familiar APIs, but `#![no_std]` and `#![forbid(unsafe_code)]`.

Co-authored-by: tnballo <tnballo@users.noreply.github.com>

README.md

@@ -975,6 +975,7 @@ Work in progress drivers. Help the authors make these crates awesome!
 1. [qemu-exit]: Quit a running QEMU session with user-defined exit code. Useful for unit or integration tests using QEMU. - ![crates.io](https://img.shields.io/crates/v/qemu-exit.svg)
 1. [RampMaker](https://crates.io/crates/ramp-maker): Stepper Motor Acceleration Ramp Generator - ![crates.io](https://img.shields.io/crates/v/ramp-maker.svg)
 1. [register-rs](https://github.com/rust-embedded/register-rs): Unified interface for MMIO and CPU registers. Provides type-safe bitfield manipulation. `register-rs` is Tock registers with added support for CPU register definitions using the same API as for the MMIO registers. This enables homogeneous interfaces to registers of all kinds. - ![crates.io](https://img.shields.io/crates/v/register.svg)
+1. [scapegoat](https://crates.io/crates/scapegoat): Safe, stack-only alternative to `BTreeSet` and `BTreeMap`. - [![crates.io](https://img.shields.io/crates/v/scapegoat.svg)](https://crates.io/crates/scapegoat)
 1. [scroll](https://crates.io/crates/scroll): extensible and endian-aware Read/Write traits for generic containers - ![crates.io](https://img.shields.io/crates/v/scroll.svg)
 1. [smbus-pec](https://crates.io/crates/smbus-pec): Minimal portable System Management Bus Packet Error Code calculation algorithm. ![crates.io](https://img.shields.io/crates/v/smbus-pec.svg)
 1. [smoltcp](https://github.com/m-labs/smoltcp): a small TCP/IP stack that runs without `alloc`. ![crates.io](https://img.shields.io/crates/v/smoltcp.svg)