update changelog for v1.9.0 release

CHANGELOG.md

@@ -1,5 +1,38 @@
 # Changelog
 
+## [Unreleased]
+
+
+## [1.9.0] 2025-01-03
+
+### Fixed
+- No longer strip `r#` prefix from `break` and `continue` labels [#6411](https://github.com/rust-lang/rustfmt/issues/6411)
+  ```rust
+  fn main() {
+      'r#if: {
+          break 'r#if;
+      }
+  }
+  ```
+- Fix panic when sorting imports [#6333](https://github.com/rust-lang/rustfmt/issues/6333)
+- Fix issue with `wrap_comments` invalidating code blocks [#6417](https://github.com/rust-lang/rustfmt/pull/6417)
+- No longer remove closure block label within a macro call [#6465](https://github.com/rust-lang/rustfmt/issues/6465)
+
+### Changed
+- Stabilize `style_edition=2024` and stabilize the `style_edition` command line option [#6431](https://github.com/rust-lang/rustfmt/pull/6431) [rust-lang/rust#134929](https://github.com/rust-lang/rust/pull/134929)
+- Apply version sorting to module declarations when using `style_edition=2024` [#6368](https://github.com/rust-lang/rustfmt/pull/6368)
+- When users set the deprecated `version` config, rustfmt now gives a hint about which equivalent `style_edition` they should use [#6361](https://github.com/rust-lang/rustfmt/pull/6361)
+- Correct version chunk splitting in the internal version sort algorithm [#6407](https://github.com/rust-lang/rustfmt/pull/6407)
+- Extend support for single line let-chain formatting to include cases where the left hand side operand is a literal, in alignment with finalized style rules as part of let-chain stabilization [#6492](https://github.com/rust-lang/rustfmt/pull/6492)
+- Begin initial formatting for `use closures` and `use chains` (`#![feature(ergonomic_clones)]`). Previously, the closure and chain was left as the developer wrote it [#6532](https://github.com/rust-lang/rustfmt/pull/6532)
+
+### Added
+- Add `style_edition=2027` to gate unstable formatting [#6324](https://github.com/rust-lang/rustfmt/pull/6324)
+- Support discovering and formatting files via external mods imported within `cfg_match`, similar to `cfg_if` behavior [#6522](https://github.com/rust-lang/rustfmt/pull/6522)
+- Add new nightly-only `match_arm_indent` option [#6525](https://github.com/rust-lang/rustfmt/pull/6525)
+  - more details in the [configuration section for this new option](https://github.com/rust-lang/rustfmt/blob/master/Configurations.md#match_arm_indent)
+
+
 ## [1.8.0] 2024-09-20
 
 ### Fixed