Add data attributions & spyndex ref

[lalligagger]

We would like to include data attributions for the current map display. Might as well link the index ref too (outside of map), if used.

[ivandorte]

For spyndex we can add an information box with:

• Short name (e.g NDVI)
• Full name (e.g. Normalized difference vegetation index)
• Domain of application (e.g. vegetation)
• Latex formula
• Reference/contributors
• Bands/constants etc...

We will also have to add the correct attribution for Copernicus and element84 .

[ivandorte]

I've added a simple FloatPanel #17 that shows:

[lalligagger]

Good for now, thanks!