Add global var to eslint config

[kaitmore]

I saw some eslint warnings about undefined globals in the hello-world.spec.js file:

❯ yarn lint
yarn run v1.22.17
$ eslint .

/Users/kaitm/Exercism/wasm/hello-world/hello-world.spec.js
  12:24  error  'WebAssembly' is not defined  no-undef
  26:26  error  'WebAssembly' is not defined  no-undef
  27:31  error  'WebAssembly' is not defined  no-undef

Adding WebAssembly to eslint globals fixed it for me:

// .eslintrc
  "globals": {
    "WebAssembly": true
  },