Update CHANGELOG

Merge pull request formal-land#186 from clarus/release-2.5.1

Release 2.5.1

Merge pull request formal-land#170 from clarus/fix-recursive-records

Avoid an infinite loop for recursive records

Merge pull request formal-land#169 from clarus/add-dune-2.8

Upgrade to Merlin 3.4.2

Merge pull request formal-land#158 from clarus/ocaml-4.10

Ocaml 4.10

Merge pull request formal-land#151 from clarus/prepare-2.3.0-release

Update the changelog for the 2.3.0 release

Merge pull request formal-land#139 from clarus/update-the-changelog-f…

…or-2.2.1

Update the changelog with the build changes

Merge pull request formal-land#135 from clarus/coq-optional

Set Coq as an optional dependency

Merge pull request formal-land#122 from clarus/2.1.0-release

Update changelog for the release

Merge pull request formal-land#107 from clarus/explicit-opam-file-nam…

…e-in-readme

Explicit opam file name in the README