web: enable http2 support

doc/debian/jitsi-meet/jitsi-meet.example

@@ -43,8 +43,8 @@ server {
     }
 }
 server {
-    listen 443 ssl;
-    listen [::]:443 ssl;
+    listen 443 ssl http2;
+    listen [::]:443 ssl http2;
     server_name jitsi-meet.example.com;
 
     # Mozilla Guideline v5.4, nginx 1.17.7, OpenSSL 1.1.1d, intermediate configuration