Add Architectures section to README

Solves: 
Notice: Skipping acquire of configured file 'stable/binary-i386/Packages' as repository 'https://xlibre-debian.github.io/devuan main InRelease' doesn't support architecture 'i386'

The xlibre repo does not support the i386 architecture, thus it shows this message every time you `sudo apt update`, which is kinda annoying.

Author: aKqir24

README.md

@@ -15,6 +15,7 @@ Types: deb
 URIs: https://xlibre-debian.github.io/devuan/
 Suites: main
 Components: stable
+Architectures: amd64
 Signed-By: /usr/share/keyrings/NexusSfan.pgp
 EOF
 
@@ -30,4 +31,4 @@ sudo apt-get update
 sudo apt-get remove xlibre xserver-xlibre* nexussfan-archive-keyring
 sudo apt-get install xorg
 sudo rm -f /etc/apt/sources.list.d/xlibre-debian.sources
-```
+```