Update fonts

Update the bundled Open Sans fonts using
<https://gwfh.mranftl.com/fonts/open-sans?subsets=latin,latin-ext>

These include Regular and Italic and Bold (700) and Bold (700) Italic
for the latin and latin extended character sets.

This removes the older WOFF format font and we now only use WOFF2 fonts.

WOFF2 offers better compression amongst other things. It is supported by
all modern browsers...

  Edge (since version 14)
  Google Chrome (since version 36)
  Firefox (since version 35)
  Opera (since version 26)
  Safari (since version 10)

Closes: #109
Reviewed-by: Dan Callahan <d.callahan@f5.com>
Signed-off-by: Andrew Clayton <a.clayton@nginx.com>

Author: ac000

source/theme/layout.html

@@ -30,12 +30,46 @@
 <meta property="twitter:card" content="summary_large_image">
 
 <style>
+/* open-sans-regular - latin_latin-ext */
 @font-face {
-    font-family: 'Open Sans';
-    src: local('OpenSans'), local('Open Sans'), local('Open Sans Regular'), local('OpenSans-Regular'),
-         url('{{ pathto('_static/OpenSans.woff2', 1) + '?' + md5('theme/static/OpenSans.woff2') }}') format('woff2'),
-         url('{{ pathto('_static/OpenSans.woff', 1) + '?' + md5('theme/static/OpenSans.woff') }}') format('woff');
+  font-display: swap;
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 400;
+  src: local('OpenSans'), local('Open Sans'), local('Open Sans Regular'), local('OpenSans-Regular'),
+       url('{{ pathto('/_static/open-sans-v40-latin_latin-ext-regular.woff2', 1) + '?' + md5('theme/static/open-sans-v40-latin_latin-ext-regular.woff2') }}') format('woff2');
 }
+
+/* open-sans-italic - latin_latin-ext */
+@font-face {
+  font-display: swap;
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 400;
+  src: local('OpenSansItalic'), local('Open Sans Italic'), local('OpenSans Italic'), local('OpenSans-Italic'),
+       url('{{ pathto('/_static/open-sans-v40-latin_latin-ext-italic.woff2', 1) + '?' + md5('theme/static/open-sans-v40-latin_latin-ext-italic.woff2') }}') format('woff2');
+}
+
+/* open-sans-700 - latin_latin-ext */
+@font-face {
+  font-display: swap;
+  font-family: 'Open Sans';
+  font-style: normal;
+  font-weight: 700;
+  src: local('OpenSansBold'), local('Open Sans Bold'), local('OpenSans Bold'), local('OpenSans-Bold'),
+       url('{{ pathto('/_static/open-sans-v40-latin_latin-ext-700.woff2', 1) + '?' + md5('theme/static/open-sans-v40-latin_latin-ext-700.woff2') }}') format('woff2');
+}
+
+/* open-sans-700italic - latin_latin-ext */
+@font-face {
+  font-display: swap;
+  font-family: 'Open Sans';
+  font-style: italic;
+  font-weight: 700;
+  src: local('OpenSansBoldItalic'), local('Open Sans Bold Italic'), local('OpenSans Bold Italic'), local('OpenSans-BoldItalic'), local('OpenSans-Bold-Italic'),
+       url('{{ pathto('/_static/open-sans-v40-latin_latin-ext-700italic.woff2', 1) + '?' + md5('theme/static/open-sans-v40-latin_latin-ext-700italic.woff2') }}') format('woff2');
+}
+
 </style>
 <link rel="stylesheet" href="{{ pathto('_static/' + styles[-1], 1) + '?' + md5('theme/static/' + styles[-1]) }}" />
 <link rel="icon" href="{{ pathto('_static/icon.png', 1) + '?' + md5('theme/static/icon.png') }}" />