Add example of detached threads and a warning about GC joining joinable thread if they haven't been joined.

README.md

@@ -58,10 +58,21 @@ Example usage
 		return ...
 	]]
 	
+	-- create detached child thread.
+	local thread = llthreads.new(thread_code, "number:", 1234, "nil:", nil, "bool:", true)
+	-- start non-joinable detached child thread.
+	assert(thread:start(true))
+	-- Use a detatched child thread when you don't care when the child finishes.
+
 	-- create child thread.
 	local thread = llthreads.new(thread_code, "number:", 1234, "nil:", nil, "bool:", true)
 	-- start joinable child thread.
 	assert(thread:start())
+	-- Warning: If you don't call thread:join() on a joinable child thread, it will be called
+	-- by the garbage collector, which may cause random pauses/freeze of the parent thread.
 	print("PARENT: child returned: ", thread:join())
 
+	local socket = require"socket"
+	socket.sleep(2) -- give detached thread some time to run.
+