docs: Add note suggesting WSL should have 16GB of swap space (#1310)

Author: finleyjb

runtime/contributing/building_from_source.md

@@ -154,7 +154,8 @@ it refers to Python 3.
 
 The easiest way to build Deno is by using a precompiled version of V8.
 
-_For WSL make sure you have sufficient memory allocated in `.wslconfig`_
+_For WSL make sure you have sufficient memory allocated in `.wslconfig`. It is
+recommended that you allocate at least 16GB._
 
 ```console
 cargo build -vv