Switch to a light/dark theme on the Faust.js documentation website

[marcusdevcode]

I struggle to read documentation because of dark mode.

[ahuseyn]

Hi @marcusdevcode, thanks for reaching out and bringing this to our attention. Accessibility is a top priority for us and we will consider this issue in our future development. In the meantime, we'll keep this ticket open for visibility; if you or anyone from the community would like to submit a PR for this, we would welcome the contribution.