test: add source for test.wasm

The original commit 74e7a4a
("test: add basic WebAssembly test") references the source for
test.wasm and while there are tools to go from wasm to wat but
having the source viewable is helpful I think.

PR-URL: nodejs#21082
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Lance Ball <lball@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: John-David Dalton <john.david.dalton@gmail.com>

test/fixtures/test.wat

@@ -0,0 +1,10 @@
+;; Compiled using the WebAssembly Tootkit (https://github.com/WebAssembly/wabt)
+;; $ wat2wasm test.wat -o test.wasm
+(module
+  (func $add (export "add") (param $first i32) (param $second i32) (result i32)
+    get_local $first
+    get_local $second
+    (i32.add)
+  )
+  (export "addTwo" (func $add))
+)