chore(env): update .env.example for staging environment and add new configuration variables

Author: wax911

on-the-edge/.env.example

@@ -39,4 +39,11 @@ OTEL_EXPORTER_OTLP_METRICS_ENDPOINT="http://otel-collector:4318/v1/metrics"
 OTEL_EXPORTER_OTLP_TRACES_ENDPOINT="http://otel-collector:4318/v1/traces"
 OTEL_EXPORTER_OTLP_LOGS_ENDPOINT="http://otel-collector:4318/v1/logs"
 
-DENO_ENV=production
+# staging/production
+DENO_ENV=staging
+
+SEGMENT_KEY=SEGMENT_KEY
+
+CLIENT_REQUEST_TIMEOUT=5000
+
+REDIS_URL=redis://default:admin@redis:6379