CSSOptions include?: RegExp; issue
Hi, 

I just need the .scss file to be exported to the output path but It doesn't work (I don't need .less, .styl, .css, etc).

Simple javascript work as expected (just to test the regex) as used in utils.ts: 
```
const filePath = 'hello.scss';
if ((new RegExp('scss$')).test(filePath)) {
  alert('it is a scss file');
} else {
  alert('it is not a scss file, add to removeFiles array');
}
```
My full code:
```
const svgtofont = require('svgtofont');
const path = require('path');
const CSSOptions = {
    include: "scss$",
    output: 'src/css',
  };

svgtofont({
  src: path.resolve(process.cwd(), '../public/assets/icons'), // svg path
  dist: path.resolve(process.cwd(), '../public/assets/fonts'), // output path
  fontName: 'icons', // font name
  classNamePrefix: "icon",
  svgicons2svgfont: {
    fontHeight: 1000,
    normalize: true
  },
  css: CSSOptions, 
}).then(() => {
  //console.log('done!');
});
```
