Add basic PKGBUILD for building on Arch/Manjaro

PKGBUILD format is described on the Arch wiki
https://wiki.archlinux.org/index.php/Creating_packages

Arch User Repository is described here
https://wiki.archlinux.org/index.php/Arch_User_Repository

The AUR package can be found here
https://aur.archlinux.org/packages/ovras/

Readme.md

@@ -19,6 +19,7 @@ Adds an overlay to the OpenVR dashboard that allows access to advanced settings
      * [Standalone](#standalone)
   * [Linux](#linux)
      * [AppImage](#appimage)
+     * [Arch/Manjaro](#archmanjaro)
      * [Building from Source](#building-from-source)
   * [Bindings](#bindings)
      * [Music](#music)
@@ -107,6 +108,11 @@ Simply double click the AppImage once downloaded to run it. Depending on your di
 
 If the AppImage doesn't work for whatever reason, please create an issue [here](https://github.com/OpenVR-Advanced-Settings/OpenVR-AdvancedSettings/issues/new/choose) describing the problem and try compiling from source.
 
+### Arch/Manjaro
+
+OpenVR Advanced Settings is on the [Arch User Repository](https://wiki.archlinux.org/index.php/Arch_User_Repository) as `ovras`.
+Manjaro users can [enable](https://wiki.manjaro.org/index.php/Arch_User_Repository) the AUR and install this package using `pamac build ovras`.
+
 ### Building from Source
 
 Detailed instructions are available [here](docs/building_for_linux.md).