fix(docs): fix popover examples (#503)

Author: nnixaa

src/playground/popover/popover-placements.component.html

@@ -1,25 +1,23 @@
-<div class="btn-group btn-divided-group btn-outline-divided-group">
-  <button class="btn btn-outline-primary" nbPopover="Right Popover!" nbPopoverPlacement="right">
-    Right
-  </button>
+<button class="btn btn-outline-primary" nbPopover="Right Popover!" nbPopoverPlacement="right">
+  Right
+</button>
 
-  <button class="btn btn-outline-primary" nbPopover="Bottom Popover!" nbPopoverPlacement="bottom">
-    Bottom
-  </button>
+<button class="btn btn-outline-primary" nbPopover="Bottom Popover!" nbPopoverPlacement="bottom">
+  Bottom
+</button>
 
-  <button class="btn btn-outline-primary" nbPopover="Top Popover!" nbPopoverPlacement="top">
-    Top
-  </button>
+<button class="btn btn-outline-primary" nbPopover="Top Popover!" nbPopoverPlacement="top">
+  Top
+</button>
 
-  <button class="btn btn-outline-primary" nbPopover="Left Popover!" nbPopoverPlacement="left">
-    Left
-  </button>
+<button class="btn btn-outline-primary" nbPopover="Left Popover!" nbPopoverPlacement="left">
+  Left
+</button>
 
-  <button class="btn btn-outline-primary" nbPopover="Start Popover!" nbPopoverPlacement="start">
-    Start
-  </button>
+<button class="btn btn-outline-primary" nbPopover="Start Popover!" nbPopoverPlacement="start">
+  Start
+</button>
 
-  <button class="btn btn-outline-primary" nbPopover="End Popover!" nbPopoverPlacement="end">
-    End
-  </button>
-</div>
+<button class="btn btn-outline-primary" nbPopover="End Popover!" nbPopoverPlacement="end">
+  End
+</button>

src/playground/popover/popover-placements.component.ts

@@ -10,6 +10,15 @@ import { Component } from '@angular/core';
 @Component({
   selector: 'nb-popover-placements',
   templateUrl: './popover-placements.component.html',
+  styles: [`
+    :host {
+      margin: 2rem 0;
+      display: block;
+    }
+    .btn {
+      margin: 1rem;
+    }
+  `],
 })
 export class NbPopoverPlacementsComponent {
 }

src/playground/popover/popover-showcase.component.html

@@ -1 +1 @@
-<button class="btn btn-outline-primary" nbPopover="Hi, I'm popover!" nbPopoverPlacement="bottom">String Test</button>
+<button class="btn btn-outline-primary" nbPopover="Hi, I'm popover!" nbPopoverPlacement="bottom">Open Popover</button>