docs: Add information about chezmoi_modify_manager

assets/chezmoi.io/docs/links/related-software.md

@@ -29,3 +29,9 @@ chezmoi plugin for asdf version manager.
 
 An add-on to synchronize your colorschemes across systems and allow easy
 colorscheme switching using chezmoi templates.
+
+### [`github.com/VorpalBlade/chezmoi_modify_manager`](https://github.com/VorpalBlade/chezmoi_modify_manager)
+
+An add-on to deal with config files that contain a mix of settings and
+transient state, such as with GUI program settings files also containing
+recently used files and window positions.

assets/chezmoi.io/docs/user-guide/manage-different-types-of-file.md

@@ -80,6 +80,15 @@ substituted with:
 current-context: {{ output "kubectl" "config" "current-context" | trim }}
 ```
 
+!!! hint
+
+    For managing ini files with a mix of settings and state (such as recently
+    used files or window positions), there is a third party tool called
+    `chezmoi_modify_manager` that builds upon `modify_` scripts. See
+    [related software](../links/related-software.md#githubcomvorpalbladechezmoi_modify_manager)
+    for more information.
+
+
 ## Manage a file's permissions, but not its contents
 
 chezmoi's `create_` attributes allows you to tell chezmoi to create a file if