Add pacman support for Arch Linux systems

- Detect netbird installed via pacman
- Remove netbird packages using pacman -Rns when replacing with binary install
- Update README to document pacman support

netbird-install-update/netbird-install-update.sh

@@ -298,6 +298,10 @@ detect_install() {
         fi
         return
     fi
+    if pacman -Q netbird &>/dev/null; then
+        echo "pkg:pacman"
+        return
+    fi
 
     echo "bin"
 }
@@ -382,6 +386,7 @@ case "$1" in
     dnf)        dnf remove -y netbird netbird-ui 2>/dev/null || true ;;
     zypper)     zypper remove -y netbird netbird-ui 2>/dev/null || true ;;
     rpm-ostree) rpm-ostree uninstall -y netbird netbird-ui 2>/dev/null || true ;;
+    pacman)     pacman -Rns --noconfirm netbird netbird-ui 2>/dev/null || true ;;
 esac
 USE_BIN_INSTALL=true SKIP_UI_APP=true bash /tmp/.netbird_install.sh
 chown root:root /usr/bin/netbird 2>/dev/null || true