Update CHANGELOG.md with v0.71.0 release notes (open-telemetry#2634)

Author: crobert-1

CHANGELOG.md

@@ -6,6 +6,17 @@
 
 This Splunk OpenTelemetry Collector release includes changes from the [opentelemetry-collector v0.71.0](https://github.com/open-telemetry/opentelemetry-collector/releases/tag/v0.71.0) and the [opentelemetry-collector-contrib v0.71.0](https://github.com/open-telemetry/opentelemetry-collector-contrib/releases/tag/v0.71.0) releases where appropriate.
 
+### 💡 Enhancements 💡
+- [Added the fluentforwarder receiver to the default ECS/EC2 configuration.](https://github.com/signalfx/splunk-otel-collector/pull/2537)
+- [Added the PostgreSQL receiver](https://github.com/signalfx/splunk-otel-collector/pull/2564)
+- [Zero config support added for always on profiling.](https://github.com/signalfx/splunk-otel-collector/pull/2538)
+- [Upgraded to include changes from SignalFx Smart Agent v5.27.3](https://github.com/signalfx/signalfx-agent/releases/tag/v5.27.3)
+- [Upgraded to the latest Java agent version v1.21.0](https://github.com/signalfx/splunk-otel-java/releases/tag/v1.21.0)
+- Third party dependency updates.
+
+### 🧰 Bug fixes 🧰
+- [Added the smartagent extension to the default agent config to properly source environment variables.](https://github.com/signalfx/splunk-otel-collector/pull/2599)
+
 ## v0.70.0
 
 This Splunk OpenTelemetry Collector release includes changes from the [opentelemetry-collector v0.70.0](https://github.com/open-telemetry/opentelemetry-collector/releases/tag/v0.70.0) and the [opentelemetry-collector-contrib v0.70.0](https://github.com/open-telemetry/opentelemetry-collector-contrib/releases/tag/v0.70.0) releases where appropriate.