Add RSPAMD_NEURAL env

PR - docker-mailserver/docker-mailserver#3833
Also mentioned in
docker-mailserver/docker-mailserver#3913

Signed-off-by: Aldo Maria Vizcaino <aldo.vizcaino87@gmail.com>

Author: AlMaVizca

charts/docker-mailserver/values.yaml

@@ -102,6 +102,7 @@ deployment:
     RSPAMD_GREYLISTING: 0
     RSPAMD_HFILTER: 1
     RSPAMD_HFILTER_HOSTNAME_UNKNOWN_SCORE: 6
+    RSPAMD_NEURAL: 0
     ENABLE_AMAVIS: 0
     AMAVIS_LOGLEVEL: 0
     ENABLE_DNSBL: 0