add compile from sources fallback to unsupported OS message

Author: henderkes

install.sh

@@ -59,6 +59,7 @@ esac
 
 if [ -z "${THE_ARCH_BIN}" ]; then
 	echo "❗ FrankenPHP is not supported on ${OS} and ${ARCH}"
+	echo "❗ You can attempt to compile from sources by following the documentation at: https://frankenphp.dev/docs/compile/"
 	exit 1
 fi