Fix syntax highlighting for type declarations

Author: markerikson

docs/api/configureStore.md

@@ -9,7 +9,7 @@ hide_title: true
 
 A friendlier abstraction over the standard Redux `createStore` function. Takes a single configuration object parameter, with the following options:
 
-```js
+```ts
 function configureStore({
     // A single reducer function that will be used as the root reducer,
     // or an object of slice reducers that will be passed to combineReducers()

docs/api/createReducer.md

@@ -9,7 +9,7 @@ hide_title: true
 
 A utility function to create reducers that handle specific action types, similar to the example function in the ["Reducing Boilerplate" Redux docs page](https://redux.js.org/recipes/reducing-boilerplate#generating-reducers). Takes an initial state value and an object that maps action types to case reducer functions. Internally, it uses the [`immer` library](https://github.com/mweststrate/immer), so you can write code in your case reducers that mutates the existing `state` value, and it will correctly generate immutably-updated state values instead.
 
-```js
+```ts
 function createReducer(
   initialState: State,
   actionsMap: Object<String, Function>

docs/api/createSelector.md

@@ -11,7 +11,7 @@ The `createSelector` utility from the [`selectorator` library](https://github.co
 
 For more specifics, see the [`selectorator` usage documentation](https://github.com/planttheidea/selectorator#usage).
 
-```js
+```ts
 function createSelector(
     // Can either be:
     //    - An array containing selector functions, string keypaths, and argument objects