fix: opentype font format

[SaltyAom]

Objective

Fix Opentype Font doesn't display correctly.

Problem

Local Opentype Font doesn't show with this plugin because of wrong CSS format generation.
Instead of generating otf font as opentype it's currently generated as otf, results in unable to display the fonts on all major browser (see attachment below)

@font-face {
  font-family: 'XKCD';
  // ❌ Wrong
  src: url('/6/src/assets/fonts/xkcd.otf') format('otf'), local('XKCD');
  // ✅ Correct
  src: url('/6/src/assets/fonts/xkcd.otf') format('opentype'), local('XKCD');
}

Currently:

This PR:

[isaac-pj]

I needed to convert the font from *.otf to *.ttf, because of this bug