[README] Fibirl uses spawn/sync as keywords (and no longer fork/join)

README.md

@@ -24,11 +24,11 @@ emper_fibril auto fib(int n) -> int {
 	Fibril fibril;
 	int a, b;
 
-	fibril.fork(&a, fib, n - 1);
+	fibril.spawn(&a, fib, n - 1);
 
 	b = fib(n - 2);
 
-	fibril.join();
+	fibril.sync();
 
 	return a + b;
 }