Edit blog post about assets

[agstephens]

See: https://github.com/cedadev/tech-blog/blob/article/asset-search/_posts/stac/2022-02-04-asset-search.md

Edit/tidy sections on:

• [x] Kerchunk - tidy this section and make it more powerful
• [x] Change last sentence to be more general.

[agstephens]

Done