[simple-scan] Arch Linux dependencies added

[Bartosz <bkosiorek src gnome org>]

commit d82daa4e25e19e515e5d00d93333937031190ca5
Author: Jacob Emery <hmpl posteo org>
Date:   Mon May 18 15:20:09 2020 +0000

    Arch Linux dependencies added

 README.md | 5 +++++
 1 file changed, 5 insertions(+)
---
diff --git a/README.md b/README.md
index bd5d555..3d96f55 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,11 @@ For Fedora:
 $ sudo dnf install -y meson vala gettext itstool gtk3-devel libgusb-devel colord-devel PackageKit-glib-devel 
libwebp-devel sane-backends-devel
 ```
 
+For Arch Linux:
+```
+sudo pacman -S meson vala gettext itstool gtk3 libusb colord libpackagekit-glib libwebp sane
+```
+
 Get the source:
 ```
 $ git clone https://gitlab.gnome.org/GNOME/simple-scan.git