improve docs around shared dict size

docker/nginx/nginx.conf

@@ -72,8 +72,10 @@ http {
     # proxy cache definition
     proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=skynet:10m max_size=50g min_free=100g inactive=48h use_temp_path=off;
 
-    # create a shared blocklist dictionary
-    lua_shared_dict blocklist 25m;
+    # create a shared blocklist dictionary with size of 30 megabytes
+    # estimated capacity of 1 megabyte dictionary is 3500 blocklist entries
+    # that gives us capacity of around 100k entries in 30 megabyte dictionary
+    lua_shared_dict blocklist 30m;
 
     # this runs before forking out nginx worker processes
     init_by_lua_block {