Added support for cache using mimetype

backend/templates/proxy_host.conf

@@ -1,5 +1,14 @@
 {% include "_header_comment.conf" %}
 
+map $sent_http_content_type $expires {
+    default                    off;
+    text/html                  epoch;
+    text/css                   max;
+    application/javascript     max;
+    ~image/                    max;
+    ~font/                     max;
+}
+
 {% if enabled %}
 server {
   set $forward_scheme {{ forward_scheme }};