feat(Results): add index (position) (#382)

This reveals the relative hit position, and is needed for example for analytics

src/components/Results.vue

@@ -3,7 +3,7 @@
 
     <slot name="header"></slot>
 
-    <slot v-for="result in results" :result="result">
+    <slot v-for="(result, index) in results" :result="result" :index="index">
       Result 'objectID': {{ result.objectID }}
     </slot>
 

stories/Results.stories.js

@@ -0,0 +1,38 @@
+import { previewWrapper } from './utils';
+import { storiesOf } from '@storybook/vue';
+
+storiesOf('Results', module)
+  .addDecorator(previewWrapper)
+  .add('default', () => ({
+    template: `
+      <ais-results />
+    `,
+  }))
+  .add('header & footer', () => ({
+    template: `
+      <ais-results>
+        <div slot="header">--- Header ---</div>
+        <div slot="footer">--- Footer ---</div>
+      </ais-results>
+    `,
+  }))
+  .add('with index', () => ({
+    template: `
+      <ais-results>
+        <div slot-scope="{ result, index }">
+          {{index + 1}}. {{result.objectID}}
+        </div>
+      </ais-results>
+    `,
+  }))
+  .add('all slots', () => ({
+    template: `
+      <ais-results>
+      <div slot="header">--- Header ---</div>
+      <div slot-scope="{ result, index }">
+        {{index + 1}}. {{result.objectID}}
+      </div>
+      <div slot="footer">--- Footer ---</div>
+      </ais-results>
+    `,
+  }));