docs: add nathantew14 as a contributor for code

[allcontributors[bot]]

Adds @nathantew14 as a contributor for code.

This was requested by therizhao in this comment

[skip ci]

[therizhao]

@all-contributors add @nathantew14 for code

[allcontributors[bot]]

@therizhao

@nathantew14 already contributed before to code

[therizhao]

@all-contributors add @nathantew14 for code

[allcontributors[bot]]

@therizhao

I've put up a pull request to add @nathantew14! :tada: