vellumwidget 0.4.0

• Server-to-client proxy (vellumwidget_proxy()). A Shiny app can now drive an
  already-rendered widget from the server without re-rendering it — no
  renderVellumwidget() round-trip, no lost pan/zoom. Get a handle with
  vellumwidget_proxy(outputId) (inside an observe()), then pipe it through the
  verbs:

  • vw_select() / vw_clear_selection() — set or clear the selection (projects
    across hover_group and propagates to linked / crosstalk widgets, exactly
    like a user click, and updates input$<id>_selected);
  • vw_filter() / vw_clear_filter() — cross-filter the widget (show only the
    given keys, dim the rest; display tier, data untouched);
  • vw_zoom() / vw_reset_zoom() — frame a set of keys, or restore the full view.

  All keys are the element data_ids — the same identifiers you read back through
  input$<id>_selected. This completes the two-way Shiny story begun with the
  input read-back in 0.3.0; see the expanded Using vellumwidget in Shiny article.