chore: update .env.example with cache setting

Author: atrifat

.env.example

@@ -4,4 +4,10 @@ APP_ENV=production
 LISTEN_HOST=0.0.0.0
 LISTEN_PORT=7860
 # (Required, Default: unbiased-small) Set this with detoxify model. Check list of model in detoxify github repository.
-DETOXIFY_MODEL=unbiased-small
+DETOXIFY_MODEL=unbiased-small
+
+# (Optional. Default: false. Options: true or false) Check whether the cache will be enabled or not
+ENABLE_CACHE=false
+
+# (Optional. Default: 60. Options: integer value) Duration of cache in seconds. Parameter will be used when the cache is enabled
+CACHE_DURATION_SECONDS=60