createFontStack: Add original fallback name & quote in declaration

Two improvements to createFontStack API:

createFontStack: Append original fallback font name to the font stack

The fontFamily returned from createFontStack now includes the original fallback font name(s). These are appended to the end of the font stack in the case the preferred font and generated fallbacks are not available.

import lobster from '@capsizecss/metrics/lobster';
import arial from '@capsizecss/metrics/arial';

const { fontFamily } = createFontStack([
  lobster,
  arial,
]);

Where fontFamily is now:

- `Lobster, 'Lobster Fallback: Arial'`
+ `Lobster, 'Lobster Fallback: Arial', Arial`

createFontStack: Quote `font-family` in `@font-face` declaration if needed

Previously, when using fontFaceFormat: 'styleObject', the generated fallback name was not quoted as necessary within the @font-face declaration. This could cause issues if the font family name contained spaces or other characters that required quoting.

seek-oss / capsize