Add TODO about using `switch` instruction

wasm/proposals/suspend_fun_with_stack_switching.md

diff --git a/wasm/proposals/suspend_fun_with_stack_switching.md b/wasm/proposals/suspend_fun_with_stack_switching.md
index e77b7a4..2136c29 100644
--- a/wasm/proposals/suspend_fun_with_stack_switching.md
+++ b/wasm/proposals/suspend_fun_with_stack_switching.md
@@ -156,6 +156,10 @@
   * could be fully managed on call site???
   * for multithreading, it should be thread local
 
+### Using `switch` instruction
+TODO
+* Can we implement same things with switch instruction?
+* May a such implementation be more performant? 
 
 ## Useful links
 * https://kotlinlang.org/docs/coroutines-overview.html