make peerDependency on typescript optional

[nilzona]

If a library like e.g. eslint-plugin-jest is built with typescript and depends on tsutils, then you will get an "unmet peer dependency" warning on typescript if you use that library in a non-ts project.

This can be solved by making the peerDependency on typescript optional in package.json like the @typescript-eslint/* projects. An example can be found here

 "peerDependenciesMeta": {
    "typescript": {
      "optional": true
    }
  },

[cschroedl-gov]

This may be related to, or a potential duplicate of #134