How to create Notification Alert like facebook without using chrome webstore?
<p>Facebook have done a great work in <strong>Notification</strong>.Usually we get desktop popup notification when we add the extensions from chrome webstore.But in facebook we can enable the extension without using chrome webstore.<em>Please see the image.</em>
<a href="https://i.stack.imgur.com/cM5B5.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cM5B5.png" alt="enter image description here"></a>
How we can do like that ?</p>

<p>NB:I know the code for showing notification.I want to know how we can add the extension without using chrome webstore,see the given image;facebook done it.</p>