[rs] Update readme badges
## wgpu-rs
[![Build Status](https://travis-ci.org/gfx-rs/wgpu-rs.svg)](https://travis-ci.org/gfx-rs/wgpu-rs)
[![Crates.io](https://img.shields.io/crates/v/wgpu.svg)](https://crates.io/crates/wgpu)
-[![Gitter](https://badges.gitter.im/gfx-rs/webgpu.svg)](https://gitter.im/gfx-rs/webgpu)
+[![Docs.rs](https://docs.rs/wgpu/badge.svg)](https://docs.rs/wgpu)
+[![Matrix](https://img.shields.io/matrix/wgpu:matrix.org)](https://matrix.to/#/#wgpu:matrix.org)
This is an idiomatic Rust wrapper over [wgpu-core](https://github.com/gfx-rs/wgpu). It's designed to be suitable for general purpose graphics and computation needs of Rust community. It currently only works for the native platform, in the future aims to support WASM/Emscripten platforms as well.
