Add note about sudo -E to differences-with-sudo

This was suggested in #1299

Author: squell

README.md

@@ -210,7 +210,8 @@ Exceptions to the above, with respect to your `/etc/sudoers` configuration:
 Some other notable restrictions to be aware of:
 
 * Some functionality is not supported, such as preventing shell escapes using `INTERCEPT` and
-  storing config in LDAP using `sudoers.ldap`, and `cvtsudoers`.
+  storing config in LDAP using `sudoers.ldap`, and `cvtsudoers`. This includes `sudo -E`,
+  which is [discouraged](https://www.sudo.ws/docs/troubleshooting/#why-does-sudo-modify-the-commands-environment) in original sudo.
 * Sudo-rs always uses PAM for authentication, so your system must be set up for PAM.
   Sudo-rs will use the `sudo` and `sudo-i` service configuration. This also means
   that resource limits, umasks, etc have to be configured via PAM and not through