JOSS Emulator docstring

[odunbar]

Purpose

Adding the API into the docs for #294

Turns out this requires the manifest to also be added...
See here

---

• I have read and checked the items on the review checklist.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.27%. Comparing base (acf1051) to head (14468e3).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #300      +/-   ##
==========================================
+ Coverage   88.17%   88.27%   +0.09%     
==========================================
  Files           8        8              
  Lines        1184     1185       +1     
==========================================
+ Hits         1044     1046       +2     
+ Misses        140      139       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.