Add a TagHelper for areas in links

[javiercn]

When i'm inside a razor view generated from an action outside of an area and I want to add a link to an action within an area I need to do the following:
<a asp-action="Other" asp-route-area="Bug">taghelper</a>
Given that we have asp-action and asp-controller tag helpers, we should also have an asp-area taghelpers as they are a first class concept in the framework