defineProp = (obj, prop, value) =>
      Object.defineProperty(obj, prop, {
        value,
        writable: false,
        enumerable: false, // Important for mimeTypes & plugins: `JSON.stringify(navigator.mimeTypes)`
        configurable: true
      })
Generate a convincing and functional MimeType or Plugin array from scratch.
They're so similar that it makes sense to use a single generator here.

Note: This is meant to be run in the context of the page.