In Module Options section in Docs, add example of default modifiers

[PawFV]

Hello we spent quite some time to figure out how to add a default modifier to our cloudinary provider with one of my colleagues. I created a proxy module, then my colleague created a custom provider wrapping cloudinary with our defaults... Until I figured out this is supported by default but it's not documented.

This is an example taken directly from our app.

  image: {
    provider: 'cloudinary',
    cloudinary: {
      baseURL: 'https://res.cloudinary.com/<company>/image/fetch/',
      modifiers: {
        effect: 'sharpen:100',
        quality: 'auto:best',
      },
    },
  },

This would generate the following link https://res.cloudinary.com/<company>/image/fetch/f_auto,q_auto:best,e_sharpen:100 for all images.

fix #509