Toggle/radio buttons

[lukavdplas]

This issue concerns:

• The long format / wide format buttons in the FreqTableComponent
• The graph / table buttons in the VisualizationComponent and WordModelsComponent.

The current state of these buttons is only conveyed through colours. They could set aria-pressed to indicate their state.

In both of these cases, however, the buttons are not independent toggles but a radio group (see also this radio group pattern guide), so that would be more appropriate.

Setting aria-pressed is trivial and achieves basic usability, implementing the radio group is a bit more work.