Write some text on how to how to play with the bands structure figure

[superstar54]

For the band structure, we should we write some text about how to zoom and that we can click on legend to show/hide: prepare the text

• Put the following sentence below the “download data” button and above the plotly widget:
• “Drag the plot to zoom, hover on the plot to see the controls on the top right. The home button brings you back to the recommended default zoom; use the Autoscale button to see all bands computed (e.g. including semicore states)”.
• Use the same text for bands only, PDOS only, and bands + PDOS.
• If PDOS is shown (PDOS only, and bands+PDOS), add also the sentence “Click on items in the legend to show/hide specific lines.”