Add supporting blog content on the why and how for BBQ

[JessicaGarson]

Code for this blog post #1431

[carlyrichmond]

Can you add a readme to the folder to explain which file is which and that it corresponds to the specific search labs piece? If someone finds this content first they may wonder what is going on.

[JessicaGarson]

Thanks, @carlyrichmond! I added a README and made some changes to the structure that I thought might make the code easier to work with.

[carlyrichmond]

The new structure looks better. I reworded one thing in the readme. I don't think this should be merged and made public until after the 8.18 release docs are public. Obviously this would be alongside the article too.

[JessicaGarson]

Thanks, @carlyrichmond. I committed to that suggestion. I agree on waiting on the merging; my thought was after 8.18 is public but shortly before the article is live.

[carlyrichmond]

Why was this taken out?

[JessicaGarson]

This was because we had it twice. The field is now in 06-bbq-search-8-18.json as:

"rescore_vector": {
              "oversample": 3
            }