Add changelog entry for the new documentation.

CHANGELOG.md

@@ -37,6 +37,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
 - Added operation options `add`, `substract` and `replace defined only` to the the composition plugins \[Menno Fraters; 2023-02-17; [#474](https://github.com/GeodynamicWorldBuilder/WorldBuilder/pull/474)\]
 - Added a new compositional model for subducting slab models such that ensures a smooth transition of compositional value from one part of a compositional layer to the other side of the layer. This is based on Arushi Saxena's fault composition plugin with the same name ([#356](https://github.com/GeodynamicWorldBuilder/WorldBuilder/pull/356)) \[Menno Fraters; 2023-02-18; [#477](https://github.com/GeodynamicWorldBuilder/WorldBuilder/pull/356)\]
 - If World Builder is configured with MPI it now reads input files on a single process and distributes them via MPI to other processes to reduce I/O load. This can be extended in the future to other input files. \[Rene Gassmoeller; 2023-04-13; [#480](github.com/GeodynamicWorldBuilder/WorldBuilder/pull/480)\]
+- Added a new html manual based on Sphinx, inculding a new tutorial which was designed from scratch to get new users up to speed quickly. It also contains a much structure to add cookbooks, developer and other documentation in the future. \[Menno Fraters; 2023-05-31; [#379](https://github.com/GeodynamicWorldBuilder/WorldBuilder/pull/489), [#379](https://github.com/GeodynamicWorldBuilder/WorldBuilder/issues/379) the related pull request mentioned in that issue.\]
 
 ### Changed
 - The World Builder Visualizer will now use zlib compression for vtu files by default. If zlib is not available binary output will be used. \[Menno Fraters; 2021-06-26; [#282](github.com/GeodynamicWorldBuilder/WorldBuilder/pull/282)\]