Add Arch Linux CT support and pacman integration

Add Arch Linux container support and integrate pacman into install utilities. New files: ct/archlinux.sh (container build/update script), install/archlinux-install.sh (install entrypoint), and json/archlinux.json (metadata). misc/install.func: detect_arch in detect_os, add pacman bootstrap, and implement pacman handlers for pkg_upgrade, pkg_install, pkg_remove, pkg_clean and package refresh; include openssh install path for pacman and provide a cleanup_lxc override to run pkg_clean. Enables creating/updating Arch Linux LXC containers and proper package manager handling.

install/archlinux-install.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+# Copyright (c) 2021-2026 community-scripts ORG
+# Author: MickLesk (CanbiZ)
+# License: MIT | https://github.com/community-scripts/ProxmoxVED/raw/main/LICENSE
+# Source: https://archlinux.org/
+
+source /dev/stdin <<<"$FUNCTIONS_FILE_PATH"
+color
+verb_ip6
+catch_errors
+setting_up_container
+network_check
+update_os
+
+motd_ssh
+customize
+cleanup_lxc