Support SSR mode

[Triloworld]

This won't work:

  {
    src: "nuxt-webfontloader",
    options: {
      google: {
        families: ['Montserrat:400,500,700,800:latin,latin-ext&display=swap']
      }
    }
  },

In SSR won't work either.
"nuxt": "^2.12.2",
"nuxt-webfontloader": "^1.1.0",

Include test for SSR mode

[Triloworld]

About: #35
Just maybe add a note to package that it won't support SSR :)
Or maybe this will can be a feature?