add documentation

README.md

@@ -11,6 +11,14 @@ read its [introductory article][blog] on my blog.
 
     pnpm install changelord
 
+## `changelog-next` directory
+
+If you want to mininize merge conflicts in `CHANGELOG.yml`,
+you can set the option `project.next_directory` to a directory (typically
+`./changelog-next`) that will hold yaml files containing the
+changes for the NEXT release. Each of those files is expected to
+have a list of changes.
+
 ## CLI commands
 
 ### Global options
@@ -41,6 +49,9 @@ sections.
 
 Adds an entry to the `NEXT` release.
 
+If `project.next_directory` is defined, the entry will be added to that
+directory instead of directly into `CHANGELOG.yml`.
+
     $ changelord add --type=maint added a changelog to the project.
 
 #### Options
@@ -62,6 +73,10 @@ Cuts the next release. That is, resolves the `NEXT` version number based on the
 latest version and the changes in the `NEXT` section, and sets its date as
 today. Modifies the source file with the result.
 
+If the `project.next_directory` option is present,
+all the changes in that directory are
+merged to `CHANGELOG.yml` and the files themselves are deleted.
+
 #### Options
 
 - `--dry` -- Resolves the next version but only outputs the resulting section