chore: Add POSTGRES_DATABASE details to the env file (#5180)

Co-authored-by: Pranav Raj S <pranav@chatwoot.com>

.env.example

@@ -38,6 +38,9 @@ REDIS_SENTINEL_MASTER_NAME=
 # REDIS_OPENSSL_VERIFY_MODE=none
 
 # Postgres Database config variables
+# You can leave POSTGRES_DATABASE blank. The default name of 
+# the database in the production environment is chatwoot_production
+POSTGRES_DATABASE=
 POSTGRES_HOST=postgres
 POSTGRES_USERNAME=postgres
 POSTGRES_PASSWORD=