Update README.md (#1455)

* Update README.md

Add the PARSE_DASHBOARD_COOKIE_SESSION_SECRET option explanation

* improve grammar

Co-authored-by: Tom Fox <[email protected]>

Author: 2 people

README.md

@@ -112,6 +112,8 @@ PARSE_DASHBOARD_USER_PASSWORD: "pass"
 PARSE_DASHBOARD_SSL_KEY: "sslKey"
 PARSE_DASHBOARD_SSL_CERT: "sslCert"
 PARSE_DASHBOARD_CONFIG: undefined // Only for reference, it must not exist
+PARSE_DASHBOARD_COOKIE_SESSION_SECRET: undefined // set the cookie session secret, defaults to a random string. Use this option if you want sessions to work across multiple servers, or across restarts
+
 ```
 
 ## Managing Multiple Apps