misc: readme improvements (spotDL#1380)

* misc: apt to install ffmpeg

* misc: added arch note

* Update README.md

capitalization change

Co-authored-by: Silverarmor <[email protected]>

Author: xnetcat

README.md

@@ -47,7 +47,7 @@ spotDL is being redesigned! This means we are currently not accepting new featur
 
 - [Windows Tutorial](https://windowsloop.com/install-ffmpeg-windows-10/)
 - OSX - `brew install ffmpeg`
-- Linux - `sudo snap install ffmpeg`
+- Linux - `sudo apt install ffmpeg`
 
 ### Installing spotDL
 
@@ -73,6 +73,10 @@ If you have trouble installing spotdl take a look at the extended installation g
 curl -L https://raw.githubusercontent.com/spotDL/spotify-downloader/master/termux/setup_spotdl.sh | sh
 ```
 
+#### Arch
+
+There is an Arch User Repository (AUR) package for [spotDL](https://aur.archlinux.org/packages/python-spotdl/).
+
 ## Usage
 
 - #### To download a song, run