Ability to scroll to a particular location on a page

**Problem**

On pages longer the browser's viewport, when a chunk of the page is overwritten, sometimes the browser scrolls to the top of the page. To improve UX, apps should be able to specify a location to "jump to" after an update.

**Proposal**

(Not sure if we can actually make this work reliably)

- Introduce a `ui.bookmark(name='foo')` API that can be used in a `form_card` to specify a "jump location" (rendered as `` internally).
- Introduce `meta_card.bookmark='foo'` that specifies a bookmark to "jump to" after an update (processed using `element.scrollIntoView()`).

Open to other solutions @mturoci

Start by tracing the form_card and meta_card entry points and the existing page-update scroll behavior. The issue proposes a ui.bookmark API, a meta_card.bookmark value, and scrollIntoView(); done means an update reliably lands at the requested bookmark without unexpectedly returning to the page top.

Written by the indexing model from the issue text.