Responsive line-height utilities

[simurai]

This adds responsive variants to the line-height utilities.

• .lh-[sm|md|lg|xl]-condensed-ultra
• .lh-[sm|md|lg|xl]-condensed
• .lh-[sm|md|lg|xl]-default
• .lh-[sm|md|lg|xl]-0

Bundle size changes

┌─────────────────────┬───────────┬───────┬───────────┬──────────┬──────────┬───────────┬──────────────────────────────┐
│ name                │ selectors │     ± │ gzip size │        ± │ raw size │         ± │ path                         │
├─────────────────────┼───────────┼───────┼───────────┼──────────┼──────────┼───────────┼──────────────────────────────┤
│ primer              │      3386 │  + 16 │   27.47 K │   + 90 B │ 172.64 K │   + 786 B │ dist/primer.css              │
│ core                │      2254 │  + 16 │   17.95 K │   + 92 B │ 114.15 K │   + 786 B │ dist/core.css                │
│ utilities           │      1381 │  + 16 │    8.75 K │   + 91 B │  66.76 K │   + 786 B │ dist/utilities.css           │

+ 90 B gzipped should be fine. 👍

---

Closes #993

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[skullface]

😍 Thank you @simurai!

[jonrohan]

This seems useful, and doesn't add too much bloat. I'll approve. 👍