[chore] Prepare release v0.81.0 (#8021)

The following commands were run to prepare this release:
- make chlog-update VERSION=v0.81.0
- make prepare-release GH=none PREVIOUS_VERSION=0.80.0
RELEASE_CANDIDATE=0.81.0 MODSET=beta

Author: opentelemetrybot

.chloggen/add-zstd-decompression.yaml

@@ -4,6 +4,28 @@
 
 <!-- next version -->
 
+## v0.81.0
+
+### 🛑 Breaking changes 🛑
+
+- `service`: Remove 'service.connectors' featuregate (#7952)
+
+### 💡 Enhancements 💡
+
+- `HTTPServerSettings`: Add zstd support to HTTPServerSettings (#7927)
+  This adds ability to decompress zstd-compressed HTTP requests to| all receivers that use HTTPServerSettings.
+- `cmd/builder`: Add "--skip-generate" option to make builder skip source generation (#7541)
+- `confighttp`: Add support for additional content decoders via `WithDecoder` server option (#7977)
+- `connectortest`: Add helpers to aid the construction of `connector.TracesRouter`, `connector.MetricsRouter`, and `connector.LogsRouter` instances to `connectortest`. (#7672)
+- `confighttp`: Add `response_headers` configuration option on HTTPServerSettings. It allows for additional headers to be attached to each HTTP response sent to the client (#7328)
+- `otlpreceiver, otlphttpexporter, otlpexporter, configgrpc`: Upgrade github.com/mostynb/go-grpc-compression and switch to nonclobbering imports (#7920)
+  consumers of this library should not have their grpc codecs overridden
+- `otlphttpexporter`: Treat partial success responses as errors (#6686)
+
+### 🧰 Bug fixes 🧰
+
+- `HTTPServerSettings`: Ensure requests with unsupported Content-Encoding return HTTP 400 Bad Request (#7927)
+
 ## v1.0.0-rcv0013/v0.80.0
 
 ### 🚩 Deprecations 🚩