update changelog (#151)

* update changelog

* address review comments

* Update docs/src/CHANGELOG.md

Co-authored-by: Martin Yeo <40734014+trexfeathers@users.noreply.github.com>

Co-authored-by: Martin Yeo <40734014+trexfeathers@users.noreply.github.com>

Author: stephenworsley

docs/src/CHANGELOG.md

@@ -5,6 +5,44 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## [Unreleased]
+
+This release added the ability to regrid data stored on a UGRID mesh.
+
+### Added
+
+- [PR#31](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/31)
+  [PR#32](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/32)
+  [PR#36](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/36)
+  [PR#39](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/39)
+  [PR#46](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/46)
+  [PR#55](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/55)
+  [PR#96](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/96)
+  Added the unstructured regridders `GridToMeshESMFRegridder` and
+  `MeshToGridESMFRegridder`.
+  [@stephenworsley](https://github.com/stephenworsley) with extensive review
+  work from [@abooton](https://github.com/abooton) and
+  [@jamesp](https://github.com/jamesp) with benchmarking help from
+  [@trexfeathers](https://github.com/trexfeathers)
+- [PR#130](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/130)
+  [PR#137](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/137)
+  Added functions for saving of the unstructured regridders.
+  [@stephenworsley](https://github.com/stephenworsley)
+
+## [0.3] - 2021-12-21
+
+The major change with this version was the addition of the ability to
+regrid curvilinear grids (i.e. grids with 2D arrays of coordinates).
+
+### Added
+- [PR#125](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/125)
+  Added support for curvilinear grids, i.e. cubes with 2D lat/lon coords.
+  [@stephenworsley](https://github.com/stephenworsley)
+- [PR#124](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/124)
+  Improved generation of benchmark data to allow data to be generated from
+  a common version/environment.
+  [@trexfeathers](https://github.com/trexfeathers)
+
 ## [0.2] - 2021-08-25
 
 The major change in this version is the addition of lazy regridding.
@@ -31,17 +69,3 @@ when the data is a dask array. Calculations may be parallelised via dask.
   Fixed an issue with directory naming. [@lbdreyer](https://github.com/lbdreyer)
 - [PR#83](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/83)
   Added missing docstrings. [@stephenworsley](https://github.com/stephenworsley)
-
-## [0.3] - 2021-12-21
-
-The major change with this version was the addition of the ability to
-regrid curvilinear grids (i.e. grids with 2D arrays of coordinates).
-
-### Added
-- [PR#125](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/125)
-  Added support for curvilinear grids, i.e. cubes with 2D lat/lon coords.
-  [@stephenworsley](https://github.com/stephenworsley)
-- [PR#124](https://github.com/SciTools-incubator/iris-esmf-regrid/pull/124)
-  Improved generation of benchmark data to allow data to be generated from
-  a common version/environment.
-  [@trexfeathers](https://github.com/trexfeathers)