docs: Add fish-chezmoi to related software

Now that it actually works, I'm adding my fish shell plugin that ensures
that, no matter how you have chezmoi installed, there will always be
completions.

While I was at it, I also created a wrapper function that (more or less)
replaces `chezmoi cd` with `cd (chezmoi source-path)`.

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

@@ -56,10 +56,15 @@ 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.
+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.
 
 ### [`install.doctor`](https://install.doctor)
 
 Desktop provisioning system.
+
+### [`github.com/halostatue/fish-chezmoi`](https://github.com/halostatue/fish-chezmoi)
+
+A plug-in for the Fish shell that ensures that completions are always loaded and
+a function that wraps `chezmoi cd` to not create a sub-shell.