Support the "anchor" links within the same document

[ekuleshov]

Please add support for the "anchor" links in the <a> tag:

Link to an element with a specified id within the page (like <a href="#top">)
https://www.w3schools.com/tags/att_a_href.asp

For these links (any started with #), instead of calling the onLinkTap callback, the html widget should scroll to the element with id matching one specified in the href attribute.