Separate table for fields that can be reused from other STAC definitions

[m-mohr]

I'm wondering whether we should generally add a second table for properties that could be useful and are overrides, which for example could be

• title and description
• nodata
• statistics (for different default stretching)
• proj:code, proj:wkt2, proj:projjson (to set the map projection)
• proj:bbox, bbox (to set the [default?] extent for map visualization)
• ...

Originally posted by @m-mohr in #26 (comment)