Fixes issue getify#1435 Added a note about WebAssembly

async & performance/ch5.md

@@ -353,6 +353,8 @@ The first call to `fooASM(..)` is what sets up our asm.js module with its `heap`
 
 Obviously, the nature of restrictions that make asm.js code so optimizable reduces the possible uses for such code significantly. asm.js won't necessarily be a general optimization set for any given JS program. Instead, it's intended to provide an optimized way of handling specialized tasks such as intensive math operations (e.g., those used in graphics processing for games).
 
+**Note** We now have developed WebAssembly (wasm) from asm.js, which allows us to bring the native performance to the web in a more secure way, developers just need to compile C/C++ code to the web which allows for incredible tasks to be performed in the browser that were not possible previously
+
 ## Review
 
 The first four chapters of this book are based on the premise that async coding patterns give you the ability to write more performant code, which is generally a very important improvement. But async behavior only gets you so far, because it's still fundamentally bound to a single event loop thread.