Add _Fira Sans_ woff2 files

Author: Nemo157

static/FiraSans-Medium.woff2

@@ -6,13 +6,19 @@
     font-family: 'Fira Sans';
     font-style: normal;
     font-weight: 400;
-    src: local('Fira Sans'), url("FiraSans-Regular.woff") format('woff');
+    src:
+      local('Fira Sans'),
+      url("FiraSans-Regular.woff2") format('woff2'),
+      url("FiraSans-Regular.woff") format('woff');
 }
 @font-face {
     font-family: 'Fira Sans';
     font-style: normal;
     font-weight: 500;
-    src: local('Fira Sans Medium'), url("FiraSans-Medium.woff") format('woff');
+    src:
+      local('Fira Sans Medium'),
+      url("FiraSans-Medium.woff2") format('woff2'),
+      url("FiraSans-Medium.woff") format('woff');
 }
 
 /* See SourceSerif4-LICENSE.md for the Source Serif 4 license. */