Commit missing controller

Author: RoyalIcing

lib/components_guide_web/controllers/react_typescript_controller.ex

@@ -10,7 +10,9 @@ defmodule ComponentsGuideWeb.ReactTypescriptController do
   @articles %{
     "testing" => %{title: "Testing React"},
     "forms" => %{title: "Creating Forms in React"},
+    "state-levels" => %{title: "Levels of State in React"},
     "reducer-patterns" => %{title: "React Reducer Patterns"},
+    "form-reducers" => %{title: "Form Validation with React Reducers"},
     "zero-hook-dependencies" => %{title: "Zero Hook Dependencies"},
     "hooks-concurrent-world" => %{title: "React Hooks in a Concurrent World"},
     "logical-clocks" => %{title: "Logical Clocks in React"},

lib/components_guide_web/templates/react_typescript/state-levels.html.md

@@ -0,0 +1,30 @@
+# React State
+
+## Derive local variable
+
+## useState
+
+## useReducer
+
+## useSyncExternalStore
+
+```ts
+function useIsOffline(): boolean {
+  const isOnline = useSyncExternalStore(
+    (callback: () => void) => {
+      window.addEventListener("offline", callback);
+
+      return () => {
+        window.removeEventListener("offline", callback);
+      };
+    },
+    () => navigator.onLine,
+    () => true
+  );
+  return !isOnline;
+}
+```
+
+## Root prop
+
+## createContext