Add share button to web view of model

[sliptonic]

Not talking about a share link but a way to get the URL formatted for sharing on social media.

when the page is embedded in the iframe, there's no way for a view on the freecad forum to find the url to 'view on ondsel' or to copy the link to reshare elsewhere.

We might want to permit the user to embed the view on other services so having a single button that pops out a menu of sharing links would be ideal

[sliptonic]

Add share button to web view of model