test: add source for test.wasm

The original commit 74e7a4a0
("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: https://github.com/nodejs/node/pull/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>