docs(#450): add note for CA certificate file path in Redis SSL configuration

Author: Oscaner

.env.example

@@ -84,6 +84,7 @@ REDIS_USE_SSL=false
 REDIS_SSL_CERT_REQS=CERT_NONE
 # Options: CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
 REDIS_SSL_CA_CERTS=
+# Path to the CA certificate file for SSL verification, e.g. /path/to/ca.crt
 
 # Whether to use Redis Sentinel mode.
 # If set to true, the application will automatically discover and connect to the master node through Sentinel.