Added a README to each of the plugins, giving an overview on how they work

plugins/kidex/README.md

@@ -0,0 +1,16 @@
+# Kidex
+
+A plugin to search files using the [Kidex](https://github.com/Kirottu/kidex) file indexing daemon.
+
+## Usage
+
+As long as the Kidex daemon is running, simply look up the file names.
+
+## Configuration
+
+```ron
+// <Anyrun config directory>/kidex.ron
+Config(
+  max_entries: 3,
+)
+```