site: update heading font

site/theme/static/common.less

@@ -44,7 +44,7 @@ a {
 
 .aside-container {
   padding-bottom: 50px;
-  font-family: Lato, @font-family;
+  font-family: Avenir, @font-family;
 
   &.ant-menu-inline .ant-menu-submenu-title h4,
   &.ant-menu-inline > .ant-menu-item,

site/theme/static/header.less

@@ -92,7 +92,7 @@
   border: 0;
   float: right;
   font-size: 14px;
-  font-family: Lato, @font-family;
+  font-family: Avenir, @font-family;
   font-variant: tabular-nums;
   &.ant-menu-horizontal {
     border-bottom: none;

site/theme/static/markdown.less

@@ -22,7 +22,7 @@
   font-weight: 500;
   margin-bottom: 20px;
   margin-top: 8px;
-  font-family: Lato, @font-family;
+  font-family: Avenir, @font-family;
   font-size: 30px;
   font-variant: tabular-nums;
   line-height: 38px;
@@ -43,7 +43,7 @@
 .markdown h5,
 .markdown h6 {
   color: @site-heading-color;
-  font-family: Lato, @font-family;
+  font-family: Avenir, @font-family;
   font-variant: tabular-nums;
   margin: 1.6em 0 0.6em;
   font-weight: 500;