List optional dependencies in peerDependencies + peerDependenciesMeta

[moshest]

For example in package.json:

{
  "name": "linkedom",
  "version": "0.16.1",
  "peerDependencies": {
    "canvas": ">= 2",
  },
  "peerDependenciesMeta": {
    "canvas": {
      "optional": true
    }
  }
}

Please see docs here: https://docs.npmjs.com/cli/v7/configuring-npm/package-json#peerdependenciesmeta

[WebReflection]

this "smells like a PR" 😄