Update README.md

* Add remark about this being a command line plugin
* Add remark about directory creation

README.md

@@ -4,11 +4,15 @@ Link listing for Zim
 List all links in your [Zim](http://zim-wiki.org/) notebook, prefixed
 with an `E` for existing or `M` for missing pages.
 
+This is a command line plugin for notebook maintenance or such tasks.
+The GUI is capable of displaying the full page list on its own.
+
 Installation
 ------------
 
 Download/clone this repository in your `$XDG_DATA_HOME/zim/plugins`
-(usually it is in `~/.local/share`).
+(usually it is in `~/.local/share`). If that directory doesn’t exist,
+you have to create it.
 
 Usage
 -----