Add CHANGELOG for #21

CHANGELOG.md

@@ -4,12 +4,15 @@
 
 * ![Enhancement][badge-enhancement] The `generate(path::String)` method now defaults to `"docs"` as the default path, allowing it to be simply called as `generate()` in e.g. the root directory of a package. ([#22][github-22])
 
+* ![Enhancement][badge-enhancement] The generated values for the `format` argument of `makedocs` are now consistent with the new API introduced in Documenter v0.21. ([#21][github-21])
+
 ## Version `v0.1.0`
 
 * Initial release.
 
 
 [github-22]: https://github.com/JuliaDocs/DocumenterTools.jl/pull/22
+[github-21]: https://github.com/JuliaDocs/DocumenterTools.jl/pull/21
 
 
 [badge-breaking]: https://img.shields.io/badge/BREAKING-red.svg