feat: Use deb822 APT source for armbian-config

- Replace creation of `armbian-config.list` with
  `armbian-config.sources`. This holds the same information in a newer
  format, deb822. This does not affect `armbian.list`.

See also: https://github.com/armbian/configng/pull/407

extensions/armbian-config.sh

@@ -2,8 +2,14 @@
 # and they are moved to main armbian repo periodically
 
 
-function custom_apt_repo__add_armbian-github-repo(){
-	echo "deb ${SIGNED_BY}https://github.armbian.com/configng stable main" > "${SDCARD}"/etc/apt/sources.list.d/armbian-config.list
+function custom_apt_repo__add_armbian-github-repo() {
+	cat <<- EOF > "${SDCARD}"/etc/apt/sources.list.d/armbian-config.sources
+	Types: deb
+	URIs: https://github.armbian.com/configng
+	Suites: stable
+	Components: main
+	Signed-By: "${APT_SIGNING_KEY_FILE}"
+	EOF
 }