docs: useMap demo link + improved docs (#650)

* improve docs: useMap demo link

* improve docs: useMap demo link (remove callback usage added)

* Add remove action to useMap story

README.md

@@ -132,7 +132,7 @@
   - [`useToggle` and `useBoolean`](./docs/useToggle.md) — tracks state of a boolean. [![][img-demo]](https://codesandbox.io/s/focused-sammet-brw2d)
   - [`useCounter` and `useNumber`](./docs/useCounter.md) — tracks state of a number. [![][img-demo]](https://streamich.github.io/react-use/?path=/story/state-usecounter--demo)
   - [`useList`](./docs/useList.md) — tracks state of an array.
-  - [`useMap`](./docs/useMap.md) — tracks state of an object.
+  - [`useMap`](./docs/useMap.md) — tracks state of an object. [![][img-demo]](https://codesandbox.io/s/quirky-dewdney-gi161)
 
 
 <br />

docs/useMap.md

@@ -2,22 +2,28 @@
 
 React state hook that tracks a value of an object.
 
-
 ## Usage
 
 ```jsx
 import {useMap} from 'react-use';
 
 const Demo = () => {
-  const [map, {set, reset}] = useMap({
+  const [map, {set, remove, reset}] = useMap({
     hello: 'there',
   });
 
   return (
     <div>
+      <button onClick={() => set(String(Date.now()), new Date().toJSON())}>
+        Add
+      </button>
+      <button onClick={() => reset()}>
+        Reset
+      </button>
+      <button onClick={() => remove('hello')} disabled={!map.hello}>
+        Remove 'hello'
+      </button>
       <pre>{JSON.stringify(map, null, 2)}</pre>
-      <button onClick={() => set(String(Date.now()), (new Date()).toJSON())}>Add</button>
-      <button onClick={() => reset()}>Reset</button>
     </div>
   );
 };

src/__stories__/useMap.story.tsx

@@ -4,15 +4,18 @@ import { useMap } from '..';
 import ShowDocs from './util/ShowDocs';
 
 const Demo = () => {
-  const [map, { set, reset }] = useMap({
+  const [map, { set, remove, reset }] = useMap({
     hello: 'there',
   });
 
   return (
     <div>
-      <pre>{JSON.stringify(map, null, 2)}</pre>
       <button onClick={() => set(String(Date.now()), new Date().toJSON())}>Add</button>
       <button onClick={() => reset()}>Reset</button>
+      <button onClick={() => remove('hello')} disabled={!map.hello}>
+        Remove 'hello'
+      </button>
+      <pre>{JSON.stringify(map, null, 2)}</pre>
     </div>
   );
 };