Update gitea download and switch to xz files

XZ files are downloaded
Change that any grep is replaced by jq command, and sed for " replace

Add systemd service files as samples

init.sh

@@ -1,6 +1,10 @@
 #!/usr/bin/env bash
 
 # check needed binaries
+if [ -z "$(command -v xz)" ]; then
+	echo "Missing xz application, aborting";
+	exit;
+fi;
 if [ -z "$(command -v curl)" ]; then
 	echo "Missing curl application, aborting";
 	exit;