Add a popup argument to TopoJson

[adarshsm]

Closes #1461.

The gap

GeoJson takes both tooltip= and popup=, but TopoJson only takes tooltip=. Passing popup= fails with TypeError: TopoJson.__init__() got an unexpected keyword argument 'popup'. That's what the issue asks for: TopoJson renders faster than GeoJson for the reporter's data, but they couldn't find a way to attach per-feature popups.

Per-feature popups on a TopoJson already work at render time. GeoJsonDetail.render() handles a TopoJson parent, and since #2250 test_topojson_non_collection_geometry_detail covers GeoJsonPopup(...).add_to(topojson). So the only missing piece is the constructor argument.

The change

TopoJson.__init__ gets popup=None, handled the same way it already handles tooltip:

• a GeoJsonPopup or Popup is added as a child
• a string is wrapped in a Popup

The docstring documents the new parameter. Nothing changes when popup isn't passed.

folium.TopoJson(
    topo_json,
    "objects.shape",
    popup=folium.GeoJsonPopup(fields=["name"]),
).add_to(m)

Tests

• New test_topojson_popup, parametrized over a GeoJsonPopup, a Popup and a plain string. It checks that the popup is the layer's child and that the rendered map binds it with <topojson>.bindPopup(. All three cases fail on main with the TypeError above and pass with this change.
• pytest tests (without selenium/playwright/snapshots): 397 passed. 4 failed, and the same 4 fail on unmodified main in my environment: three PNG-export tests (ImportError) and test_timedynamic_geo_json (geodatasets not installed).
• black --check and ruff check pass on the touched files.

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