Add a `BasemapSelection` component to allow the user to change the map style

[rudokemper]

Feature Request

Recently, we have established that we would like to add an option for users to explore their change detection alerts overlaid on various satellite imagery - e.g. Planet (cf. https://github.com/ConservationMetrics/guardianconnector-views/issues/44), Sentinel - backgrounds. To do this, we will need a basemap picker to change the map style as per this Mapbox API example.

Initial options may include: default Mapbox map, satellite-streets-v12 and Planet NICFI.

Implementation plan

• [x] Let's create a new component called BasemapSelector which provides a UI to toggle between different basemap options.
• [x] The component should indicate the basemap that is currently selected.
• [x] When a new basemap is selected, the component should emit a new style URL (or stylesheet definition) upstream to the parent component.
• [x] The Map and AlertsDashboard components should listen for changes in the active style URL, and repaint the map when a new style is set.
  • [x] In so doing, all of the alerts should persist to the new map style.
• [x] An option to toggle Planet NICFI should only be shown if a VIEWS_CONFIG variable PLANET_API_KEY is set.
• [x] As an initial acceptance criteria for Planet NICFI, let's load the latest monthly basemap. Follow-on work in https://github.com/ConservationMetrics/guardianconnector-views/issues/44 can then add a slider to select a specific month & year for Planet.

Inspo

Global Forest Watch:

Explorer.Land:

Esri: