docs(README.md): update.

Author: sciborrudnicki

README.md

@@ -38,7 +38,7 @@ Simple state management for TypeScript.
   * `ImmutableState`
   * [`NullState`](#nullstate)
   * [`NumberState`](#numberstate)
-  * [`State`](#state)
+  * `State`
 * [Immutability](#immutability)
   * [Sealed](#sealed)
   * [Frozen](#frozen)
@@ -426,12 +426,6 @@ numberedState.increment(5);
 numberedState.reset();
 ```
 
-### `State`
-
-```typescript
-import { State } from '@typescript-package/state';
-```
-
 ## Immutability
 
 ### Sealed