Best pratice: Provide proj:shape for thumbnails

[m-mohr]

For browser rendering it would be very beneficial to provide proj:shape also to thumbnails (and overviews) so that image dimensions are known before loading them:

{
  "href": "thumb.png",
  "title": "Thumbnail",
  "type": "image/png",
  "roles": ["thumbnail"],
  "proj:shape": [400, 400],
  "proj:epsg": null
}

See also: radiantearth/stac-browser#166