message: docs: Add separate links to nightly and stable
diff: # bottom
  [<img src="https://img.shields.io/github/workflow/status/ClementTsang/bottom/ci/master?style=flat-square&logo=github" alt="CI status">](https://github.com/ClementTsang/bottom/actions?query=branch%3Amaster)
  -[<img src="https://img.shields.io/crates/v/bottom.svg?style=flat-square" alt="crates.io">](https://crates.io/crates/bottom)
  -[<img src="https://img.shields.io/badge/docs-bottom-66c2a5?style=flat-square&labelColor=555555&logoColor=white" alt="documentation">](https://clementtsang.github.io/bottom)
  +[<img src="https://img.shields.io/crates/v/bottom.svg?style=flat-square" alt="crates.io link">](https://crates.io/crates/bottom)
  +[<img src="https://img.shields.io/badge/docs-nightly-88c0d0?style=flat-square&labelColor=555555&logoColor=white" alt="Nightly documentation">](https://clementtsang.github.io/bottom/nightly)
  +[<img src="https://img.shields.io/badge/docs-stable-66c2a5?style=flat-square&labelColor=555555&logoColor=white" alt="Stable documentation">](https://clementtsang.github.io/bottom/stable)
  A cross-platform graphical process/system monitor with a customizable interface and a multitude of features. Supports Linux, macOS, and Windows. Inspired by [gtop](https://github.com/aksakalli/gtop), [gotop](https://github.com/xxxserxxx/gotop), and [htop](https://github.com/htop-dev/htop/).
  @@ -221,6 +222,8 @@ You can also try to use the generated release binaries and manually install them
  - [Latest stable release](https://github.com/ClementTsang/bottom/releases/latest), generated off of the release branch
  - [Latest nightly version](https://github.com/ClementTsang/bottom/releases/tag/nightly), which is generated daily off of the master branch at 00:00 UTC
  +#### Auto-completion
  +
  The release binaries are packaged with shell auto-completion files for bash, fish, zsh, and Powershell. To install them:
  - For bash, move `btm.bash` to `$XDG_CONFIG_HOME/bash_completion or /etc/bash_completion.d/`.
  