Add render config to MAXAR collections

[oliverroick]

Adds "renders" config for the visual asset to each MAXAR collection.

The config looks like this:

"renders": {
  "visual": {
    "title": "Visual Image",
    "assets": [ "visual" ],
    "asset_bidx": "visual|1,2,3",
    "minmax_zoom": [8, 22]
  }
}