Add ability to set encodings

[kisenka]

Hi @sokra!
Thanks for the great loader.

Default loader behaviour is to encode source and return Data URI. But for SVG is no necessary to encode source in base64, because it works with raw content encoded with encodeURIComponent. Moreover it will decrease ~30% of content length and save browser resources for unpacking base64 string. My suggestion is to add user defined handlers to specific mime-type, something like this:

{
  module: {
    loaders: [
      {
        test: /\.(jpg|png|gif|svg)$/
        loader: 'url?limit=10000'
      }
    ]
  },
  url: {
    handlers: {
      'image/svg+xml': function (content) {
        return 'data:image/svg+xml,' + encodeURIComponent(content);
      }
    }
  }
}

For backward compatibility option can be disabled by default. For details please take a look at my advanced-url-loader which based on url-loader. I can make a PR, if you agree. Also I want be a volunteer and cover all existing loader code with tests. And close some issues.

[joekrill]

IE has issues with Base64 encoded data URIs, so I'm having problems related to this also. But I'm not sure it even needs to be as complicated as you suggest. A simple option to toggle using URL-encoded plaintext instead of Base64 encoding should be sufficient. Those are the only valid way to encode data URIs anyway (see http://codepen.io/tigt/post/optimizing-svgs-in-data-uris). Then you could just do something like:

loaders: [{ 
    test: /\.(svg)$/,
    loader: 'url?limit=10000&encoding=url'
}, {
   test: /\.(png)$/,
   loader: 'url?limit=10000&encoding=base64'
}]

[kisenka]

@joekrill good suggestion

[michael-ciniawsky]

@kisenka Sry for the delay are you still interested in a solution here ? @joekrill's comment sounds promising (add options to set encoding)

[michael-ciniawsky]

@kisenka @joekrill PR highly welcome after #70 lands 😛

[michael-ciniawsky]

#28 needs to be reworked (WIP)