message: Add pkg-config to Debian dependencies
diff: @@ -65,7 +65,7 @@ libraries to build Alacritty. Here's an apt command that should install all of
  them. If something is still found to be missing, please open an issue.
  ```sh
  -apt-get install cmake libfreetype6-dev libfontconfig1-dev xclip
  +apt-get install cmake pkg-config libfreetype6-dev libfontconfig1-dev xclip
  ```
  #### Arch Linux
  