Add OL STAC example

[m-mohr]

Adds an OL STAC example as requested in #14927

It does complain about missing dependencies. Do I need to add it do devDependencies? Edit: Yes, that seems to work. Hope that's the right way of doing it.

[github-actions]

📦 Preview the website for this branch here: https://deploy-preview-15042--ol-site.netlify.app/.

[mike-000]

Usually the region between the original image extent and the extent which encloses it when reprojected is transparent, as in https://codesandbox.io/s/multiple-cogs-forked-8ls754?file=/main.js, not black as here

This suggests you have only 3 bands or an incorrect nodata value?

[m-mohr]

Good point, OL STAC tried to default to NaN if no nodata value was provided through STAC, but that was obviously not a good idea as it discarded any nodata values from the TIFF. Fixed.

[mike-000]

Yes, I have sometimes found it necessary to add a nodata setting to force an alpha band to be added for non-parallel reprojection, but doing that unnecessarily overrides any genuine nodata. It might be better if any supplied setting was appended instead of simply overriding.

[mike-000]

#15048 will ensure alpha can be set in regions outside the original source extent without overriding the metadata. The metadata would handle alpha inside the original extent.

[m-mohr]

Updated and re-released ol-stac with ol as peer dependency.

[tschaub]

Thanks, @m-mohr