Add support for simple aggregations

[jbuckner]

There are certain fields in the aggregations (facets), particularly the year histogram facet where the data is different depending on how it is requested: "simple" facets vs json-style "advanced" facets. This adds support for both formats so we can request the year histogram independently from the other facets.

[codecov]

Codecov Report

Merging #9 (8868675) into main (27ffa10) will increase coverage by 0.22%.
The diff coverage is 100.00%.

❗ Current head 8868675 differs from pull request most recent head 7593481. Consider uploading reports for the commit 7593481 to get more accurate results

@@            Coverage Diff             @@
##             main       #9      +/-   ##
==========================================
+ Coverage   78.73%   78.96%   +0.22%     
==========================================
  Files          19       19              
  Lines        1218     1231      +13     
  Branches       24       25       +1     
==========================================
+ Hits          959      972      +13     
  Misses        258      258              
  Partials        1        1              

Impacted Files	Coverage Δ
src/search-params.ts	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 27ffa10...7593481. Read the comment docs.