fix(datetime): remove outline for focus and add ripple

packages/core/src/components/datetime/datetime.scss

@@ -22,6 +22,11 @@ ion-datetime {
 
   background: transparent;
   cursor: pointer;
+
+  &:active,
+  &:focus {
+    outline: none;
+  }
 }
 
 .datetime-text {

packages/core/src/components/datetime/datetime.tsx

@@ -627,6 +627,7 @@ export class Datetime {
         aria-disabled={this.disabled ? 'true' : false}
         onClick={this.open.bind(this)}
         class='datetime-cover'>
+        {this.mode === 'md' ? <ion-ripple-effect /> : null}
       </button>
     ];
   }