add update function

src/main.lua

@@ -823,6 +823,7 @@ while true do
         "Print Design",
         "VPrint Design",
         "Join VPrint",
+        "Update",
     }, "Select Action")
 
     if action == 1 then
@@ -969,5 +970,10 @@ while true do
         until id == masterid
         VP_printstack(buf,dimensions, cx,1,cz,0)
     end
+    if action == 5 then
+        shell.run("rm", "main.lua")
+        shell.run("wget", url)
+        return
+    end
 end