Add indicator of zoomLevel and datasetLevel to map

[clarasb]

This PR:

• adds a box to the map, that displays the current zoomLevel of the map and the current datasetLevel. The visibilty of the box can be changed in the settings. The initial visibility can be set in config.json (default: false).
• is dependent on: WebAPI: Add resolutions and spatialUnits to mldataset  xcube#1177.
• adds information on the number of levels in the selected dataset to the Info-Panel
• add feature to feature references list in the documentation

Closes #287.

[forman]

Cool feature, great job!

Please apply renamings:

• Settings state: zoomEnabled --> showZoomBox
• Branding: allowZoomBox --> showZoomBox
• In settings panel UI: "Levels" --> "Number of resolution levels"

In a new directory module ZoomBox

• Move ZoomBox.tsx
• Move ZoomBox.stories.tsx
• Add index.tsx to export ZoomBox component

[AliceBalfanz]

Suggested change

	Displays an information box that showing the current
	zoom level of the map and the dataset resolution level (particularly
	useful for multi-resolution dataset) used for displaying the dataset
	in the map.
	Displays an information box showing the current
	map zoom level and the dataset resolution level used for displaying the
	dataset on the map. The the dataset resolution level is particularly
	useful for multi-resolution datasets.

[AliceBalfanz]

Suggested change

	The visibility of this feature can be controlled in the
	The visibility of this feature can be controlled through the

[AliceBalfanz]

Works nicely! Minor comments on wording for the documentation.