haddock-project: added changelog.d entry

changelog.d/pr-9821

@@ -0,0 +1,20 @@
+synopsis: `haddock-project` support for subcomponents
+packages: cabal-install
+prs: #9821
+issues:
+significance: significant
+
+description: {
+
+- `haddock-project` handles sublibraries, test suites and benchmarks.
+- `haddock-project` subcommand installs documentation in the output directory
+  using `haddock` subcommand.
+- `haddock` receives `--package-name` flag whcih allows to set names of
+  components which are included in the main `index.html` file.
+- added `--use-unicode` flag to `haddock` and `haddock-project` commands.
+- The directory structure of `./dist-newstyle` has changed.  `haddock`
+  subcommand will install `package:sublib` component in a directory
+  `package-sublib` under `l/sublib/doc/html/`.
+
+}
+