Implement spinner for graph loading times

[bfrgottscma]

As a user I would like to get visual feedback if

• loading of the dataset/graph
• reloading of the graph (e.g to apply highlighting, apply a different layout) takes longer than expected. Please include a Basic progress-spinner in the graph and the map view.

Please include transparency to hide the background as in MibiPortal.

To discuss later when first implementation of spinner can be tested: The spinner should appear if loading takes longer than ...500ms?... to prevent it quickly flashing up, either by using a fade in or a delay.

Think of Tests

• [ ] Excel testsheet needed
• [ ] E2e test needed
• [ ] Integration test needed
• [ ] Unit test needed

[bfrgottscma]

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