message: Add Discord server link and download count to `README`
diff: # iced
  -[![Test Status](https://github.com/hecrj/iced/workflows/Test/badge.svg?event=push)](https://github.com/hecrj/iced/actions)
  [![Documentation](https://docs.rs/iced/badge.svg)][documentation]
  [![Crates.io](https://img.shields.io/crates/v/iced.svg)](https://crates.io/crates/iced)
  [![License](https://img.shields.io/crates/l/iced.svg)](https://github.com/hecrj/iced/blob/master/LICENSE)
  -[![project chat](https://img.shields.io/badge/chat-on_zulip-brightgreen.svg)](https://iced.zulipchat.com)
  +[![Downloads](https://img.shields.io/crates/d/iced.svg)](https://crates.io/crates/iced)
  +[![Test Status](https://github.com/hecrj/iced/workflows/Test/badge.svg?event=push)](https://github.com/hecrj/iced/actions)
  +[![Discord Server](https://img.shields.io/discord/628993209984614400?label=&labelColor=6A7EC2&logo=discord&logoColor=ffffff&color=7389D8)](https://discord.gg/3xZJ65GAhd)
  A cross-platform GUI library for Rust focused on simplicity and type-safety.
  Inspired by [Elm].
  