embed: true option doesn't work
Setting `embed: true` does not embed fonts in css file.

webpack:
```
      {
        test: /\.font\.js/,
        use: [
          MiniCssExtractPlugin.loader,
          'css-loader',
          {
            loader: 'webfonts-loader',
            options: {
              emitCodepoints: {
                fileName: 'svgIcons.codepoints.json',
                type: 'json'
              },
              types: ['eot', 'woff', 'woff2', 'ttf', 'svg'],
              publicPath: '/',
              fileName: 'app.[fontname].[hash].[ext]',
              writeFiles: true,
            },
          }
```
font.js

```
module.exports = {
  fontName: 'svgIcons',
  classPrefix: 'svgIcons-',
  files: ['./svg/*.svg'],
  cssDest: './assets',
  cssFontsPath: './',
  dest: 'src/client/components/atoms/SvgFontIcon/assets',
  embed: true,
};
```

output: 
```
@font-face {
	font-family: "svgIcons";
	src: url("svgIcons.eot?2a6f644fdb457b5f16166da1d810a26c?#iefix") format("embedded-opentype"),
url("svgIcons.woff?2a6f644fdb457b5f16166da1d810a26c") format("woff"),
url("svgIcons.woff2?2a6f644fdb457b5f16166da1d810a26c") format("woff2"),
url("svgIcons.ttf?2a6f644fdb457b5f16166da1d810a26c") format("truetype"),
url("svgIcons.svg?2a6f644fdb457b5f16166da1d810a26c#svgIcons") format("svg");
}

.icon {
	line-height: 1;
}

.icon:before {
	font-family: svgIcons !important;
	font-style: normal;
	font-weight: normal !important;
	vertical-align: top;
}

.svgIcons-play-circle:before {
	content: "\f101";
}
```