fix: change default theme to `plain`

examples/store/state.ts

@@ -5,6 +5,6 @@ class State extends Store.State {
     { key: "b", value: "B" },
     { key: "c", value: "C" },
   ];
-  style = Styles.plainb;
+  style = Styles.plain;
 }
 export default new State();