nginx configuration: enable caching / precompiled regular expressions

roles/matrix-nginx-proxy/templates/nginx/nginx.conf.j2

@@ -18,6 +18,8 @@ events {
 	worker_connections 1024;
 }
 
+# "PCRE JIT can speed up processing of regular expressions significantly."
+pcre_jit on;
 
 http {
 	proxy_temp_path /tmp/proxy_temp;