Replace punycode dependency with string iteration

[andersk]

Proposed changes

The spread operator has been available since Node 5.0.0, and iterates strings over their code points (not code units), as expected here. There’s no need to use the punycode library for this.

Code quality

• [ ] I made some tests for my changes
  • This is already covered by tests
• [ ] I added my name in the contributors field of the package.json file. Beware to use the same format than for the author field for the entries so that you'll get a mention in the README.md with a link to your website.

License

To get your contribution merged, you must check the following.

• [x] I read the project license in the LICENSE file
• [x] I agree with publishing under this project license

Join

• [ ] I wish to join the core team
• [ ] I agree that with great powers comes responsibilities
• [ ] I'm a nice person

My NPM username: andersk

[nfroidure]

Adding link to mozdev for reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#utf-16_characters_unicode_code_points_and_grapheme_clusters

[nfroidure]

Published under svgicons2svgfont@15.0.0 . Thanks for your help.