fix critical timer typo and make timer work

src/lib/timer.lua

@@ -1,7 +1,7 @@
 local is_callable = function(callback)
   local _type = type(callback)
   if _type == "function" then return true end
-  of _type == "table" then
+  if _type == "table" then
     local metatable = getmetatable(callback)
     return (type(metatable) == "table") and (type(metatable.__call) == "function")
   end
@@ -49,6 +49,7 @@ local new_timer = function(callback, update, ...)
 end
 
 return {
+  version = "v1.0.0-modified",
   after = function(deadline, callback, ...)
     local timer = new_timer(callback, update_after, ...)
     timer.deadline = deadline