Add building info

README.md

@@ -43,3 +43,10 @@ choosing it, while `<format>` is how it appears in chat, when formatted (colored
 After adding enough pronouns, you can pick your most preferred ones with `/nouns set <main> <secondary>`. You need to 
 pick them from the ones you added previously with the `create` subcommand, and you can read a complete list using 
 `/nouns list`.  
+  
+## Building
+The plugin's dependencies and build system are handled by Maven. Just clone this git repo and run  
+```text
+mvn clean package
+```  
+To build the plugin. You will find the `.jar` file in the `target/` directory of the git repo.