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

plugins/dictionary/README.md

@@ -0,0 +1,16 @@
+# Dictionary
+
+Look up word definitions using the [Free Dictionary API](https://dictionaryapi.dev/).
+
+## Usage
+
+Type in `<prefix><word to define>`, where prefix is the configured prefix (default in [Configuration](#Configuration)).
+
+## Configuration
+
+```ron
+// <Anyrun config dir>/dictionary.ron
+Config(
+  prefix: ":def",
+)
+```