documentation for all major modules

ChatApp/app/src/main/java/client/ClientLogin.java

@@ -13,6 +13,10 @@ public class ClientLogin {
     @FXML
     public TextField usernameField;
 
+    /**
+     * Sets the username and switches to the loading screen.
+     * @throws IOException if the FXML file is not found.
+     */
     @FXML
     private void login() throws IOException {
         String username = usernameField.getText();