Add Korean-friendly font (#1597)

* Add Korean-friendly font

* Fix directory error

* Add alternative font

css/ko.css

@@ -4,6 +4,10 @@
 */
 /* For image callouts in writing-middleware.md */
 
+@import url('../fonts/ko/Pretendard.css');
+
+html, body {font-family: Pretendard, Arial, sans-serif;}
+
 .callout {position: relative;}
 
 #callout1 {top: 40px; }

fonts/ko/pretendard.css

@@ -0,0 +1,71 @@
+/*
+Copyright (c) 2021 Kil Hyung-jin, with Reserved Font Name Pretendard.
+https://github.com/orioncactus/pretendard
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+http://scripts.sil.org/OFL
+*/
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 900;
+	font-display: swap;
+	src: local('Pretendard Black'), url(./woff2/Pretendard-Black.woff2) format('woff2'), url(./woff/Pretendard-Black.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 800;
+	font-display: swap;
+	src: local('Pretendard ExtraBold'), url(./woff2/Pretendard-ExtraBold.woff2) format('woff2'), url(./woff/Pretendard-ExtraBold.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 700;
+	font-display: swap;
+	src: local('Pretendard Bold'), url(./woff2/Pretendard-Bold.woff2) format('woff2'), url(./woff/Pretendard-Bold.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 600;
+	font-display: swap;
+	src: local('Pretendard SemiBold'), url(./woff2/Pretendard-SemiBold.woff2) format('woff2'), url(./woff/Pretendard-SemiBold.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 500;
+	font-display: swap;
+	src: local('Pretendard Medium'), url(./woff2/Pretendard-Medium.woff2) format('woff2'), url(./woff/Pretendard-Medium.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 400;
+	font-display: swap;
+	src: local('Pretendard Regular'), url(./woff2/Pretendard-Regular.woff2) format('woff2'), url(./woff/Pretendard-Regular.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 300;
+	font-display: swap;
+	src: local('Pretendard Light'), url(./woff2/Pretendard-Light.woff2) format('woff2'), url(./woff/Pretendard-Light.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 200;
+	font-display: swap;
+	src: local('Pretendard ExtraLight'), url(./woff2/Pretendard-ExtraLight.woff2) format('woff2'), url(./woff/Pretendard-ExtraLight.woff) format('woff');
+}
+
+@font-face {
+	font-family: 'Pretendard';
+	font-weight: 100;
+	font-display: swap;
+	src: local('Pretendard Thin'), url(./woff2/Pretendard-Thin.woff2) format('woff2'), url(./woff/Pretendard-Thin.woff) format('woff');
+}