Firefox implemented the menu element where you can add to the existing context menu. It was also implemented in Chrome behind a flag. Unfortunately this feature has been removed from the W3C standard due to a lack of implementation interest.

<menu type=context id=mymenu>

    <menuitem label=Refresh Post onclick=window.location.reload(); icon=/images/refresh-icon.png></menuitem>

    <menuitem label=Skip to Comments onclick=window.location='#comments'; icon=/images/comment_icon.gif></menuitem>

    <menu label=Share on... icon=/images/share_icon.gif>

        <menuitem label=Twitter icon=/images/twitter_icon.gif onclick=goTo('//twitter.com/intent/tweet?text=' + document.title + ':  ' + window.location.href);></menuitem>

        <menuitem label=Facebook icon=/images/facebook_icon16x16.gif onclick=goTo('//facebook.com/sharer/sharer.php?u=' + window.location.href);></menuitem>

    </menu>

</menu>

To make an element use this context menu, add the contextmenu=mymenu attribute to it. You can see here that mymenu matches the id attribute of the menu element.

Source

Demo