Add UDP buffer note

Author: thespad

readme-vars.yml

@@ -147,6 +147,8 @@ app_setup_block: |
 
   You should also uncomment the `Alt-Svc` header in your `ssl.conf` so that browsers are aware that you offer QUIC connectivity.
 
+  It is [recommended](https://quic-go.net/docs/quic/optimizations/#udp-buffer-sizes) to increase the UDP send/recieve buffer **on the host** by setting the `net.core.rmem_max` and `net.core.wmem_max` sysctls. Suggested values are between 4-16Mb (4194304-16777216 bytes). For persistence between reboots use `/etc/sysctl.d/`.
+
   ### Migration from the old `linuxserver/letsencrypt` image
 
   Please follow the instructions [on this blog post](https://www.linuxserver.io/blog/2020-08-21-introducing-swag#migrate).