docs: preparing 0.20 changelog for release (#9799)

Co-authored-by: Gus Eggert <[email protected]>
Co-authored-by: Marcin Rataj <[email protected]>
Co-authored-by: Henrique Dias <[email protected]>

docs/changelogs/v0.20.md

@@ -6,13 +6,111 @@
 
 - [Overview](#overview)
 - [🔦 Highlights](#-highlights)
+  - [Boxo under the covers](#boxo-under-the-covers)
+  - [HTTP Gateway](#http-gateway)
+    - [Switch to `boxo/gateway` library](#switch-to-boxogateway-library)
+    - [Improved testing](#improved-testing)
+    - [Trace Context support](#trace-context-support)
+    - [Removed legacy features](#removed-legacy-features)
+  - [`--empty-repo` is now the default](#--empty-repo-is-now-the-default)
 - [📝 Changelog](#-changelog)
 - [👨‍👩‍👧‍👦 Contributors](#-contributors)
 
 ### Overview
 
 ### 🔦 Highlights
 
+#### Boxo under the covers
+We have consolidated many IPFS repos into [Boxo](https://github.com/ipfs/boxo), and this release switches Kubo over to use Boxo instead of those repos, resulting in the removal of 27 dependencies from Kubo:
+
+- github.com/ipfs/go-bitswap
+- github.com/ipfs/go-ipfs-files
+- github.com/ipfs/tar-utils
+- gihtub.com/ipfs/go-block-format
+- github.com/ipfs/interface-go-ipfs-core
+- github.com/ipfs/go-unixfs
+- github.com/ipfs/go-pinning-service-http-client
+- github.com/ipfs/go-path
+- github.com/ipfs/go-namesys
+- github.com/ipfs/go-mfs
+- github.com/ipfs/go-ipfs-provider
+- github.com/ipfs/go-ipfs-pinner
+- github.com/ipfs/go-ipfs-keystore
+- github.com/ipfs/go-filestore
+- github.com/ipfs/go-ipns
+- github.com/ipfs/go-blockservice
+- github.com/ipfs/go-ipfs-chunker
+- github.com/ipfs/go-fetcher
+- github.com/ipfs/go-ipfs-blockstore
+- github.com/ipfs/go-ipfs-posinfo
+- github.com/ipfs/go-ipfs-util
+- github.com/ipfs/go-ipfs-ds-help
+- github.com/ipfs/go-verifcid
+- github.com/ipfs/go-ipfs-exchange-offline
+- github.com/ipfs/go-ipfs-routing
+- github.com/ipfs/go-ipfs-exchange-interface
+- github.com/ipfs/go-libipfs
+
+Note: if you consume these in your own code, we recommend migrating to Boxo. To ease this process, there's a [tool which will help migrate your code to Boxo](https://github.com/ipfs/boxo#migrating-to-box).
+
+You can learn more about the [Boxo 0.8 release](https://github.com/ipfs/boxo/releases/tag/v0.8.0) that Kubo now depends and the general effort to get Boxo to be a stable foundation [here](https://github.com/ipfs/boxo/issues/196).
+
+#### HTTP Gateway
+
+##### Switch to `boxo/gateway` library
+
+Gateway code was extracted and refactored into a standalone library that now
+lives in [boxo/gateway](https://github.com/ipfs/boxo/tree/main/gateway). This
+enabled us to clean up some legacy code and remove dependency on Kubo
+internals.
+
+The GO API is still being refined, but now operates on higher level abstraction
+defined by `gateway.IPFSBackend` interface.  It is now possible to embed
+gateway functionality without the rest of Kubo.
+
+See the [car](https://github.com/ipfs/boxo/tree/main/examples/gateway/car)
+and [proxy](https://github.com/ipfs/boxo/tree/main/examples/gateway/proxy)
+examples, or more advanced
+[bifrost-gateway](https://github.com/ipfs/bifrost-gateway).
+
+##### Improved testing
+
+We are also in the progress of moving away from gateway testing being based on
+Kubo sharness tests, and are working on
+[ipfs/gateway-conformance](https://github.com/ipfs/gateway-conformance) test
+suite that is vendor agnostic and can be run against arbitrary HTTP endpoint to
+test specific subset of [HTTP Gateways specifications](https://specs.ipfs.tech/http-gateways/).
+
+##### Trace Context support
+
+We've introduced initial support for `traceparent` header from [W3C's Trace
+Context spec](https://w3c.github.io/trace-context/).
+
+If `traceparent` header is
+present in the gateway request, one can use its `trace-id` part to inspect
+trace spans via selected exporter such as Jaeger UI
+([docs](https://github.com/ipfs/boxo/blob/main/docs/tracing.md#using-jaeger-ui),
+[demo](https://user-images.githubusercontent.com/157609/231312374-bafc2035-1fc6-4d6b-901b-9e4af039807c.png)).
+
+To learn more, see [tracing docs](https://github.com/ipfs/boxo/blob/main/docs/tracing.md).
+
+##### Removed legacy features
+
+- Some Kubo-specific prometheus metrics are no longer available.
+  - An up-to-date list of gateway metrics can be found in [boxo/gateway/metrics.go](https://github.com/ipfs/boxo/blob/main/gateway/metrics.go).
+- The legacy opt-in `Gateway.Writable` is no longer available as of Kubo 0.20.
+  - We are working on developing a modern replacement.
+    To support our efforts, please leave a comment describing your use case in
+    [ipfs/specs#375](https://github.com/ipfs/specs/issues/375).
+
+#### `--empty-repo` is now the default
+
+When creating a repository with `ipfs init`, `--empty-repo=true` is now the default. This means
+that your repository will be empty by default instead of containing the introduction files.
+You can read more about the rationale behind this decision on the [tracking issue](https://github.com/ipfs/kubo/issues/9757).
+
 ### 📝 Changelog
 
 ### 👨‍👩‍👧‍👦 Contributors
+
+