Add landcover example to data article

[edwardsmarc]

A common concern is going to be reclassifying detailed land cover data into the 1km grid from either FRI or 30m land cover rasters. Need to communicate that each land cover class can be summed into the 1km as separate layers. This loses the original spatial resolution but maintains the same area of each class.

This is preferable to actually reclassifying the raster which loses both spatial and area resolution.

Add an example of this to the Data article on the website.