create a dedicated page of the bands availalbe in SEPAL

[12rambau]

They are used in every recipe section, I think we can set them in one place and tell the user to look there.

alternatively we create a template and we include it in every recipe page

[BuddyVolly]

Thinking about it, we should add a menu at the top called features (or maybe something else). Therein we can have a something like , supported satellites, ARD types, and also band ratios and their explanation. Basically things that are redundant within various recipes

[12rambau]

the feature section have been created in 6ef9309, and a band.rst file is now waiting to be populated ;-)