Add missing reference material on report-splitting (#652)

Adds docstring for `get_reports`, add more `@docs`.

Author: timholy

docs/src/optanalysis.md

@@ -237,6 +237,14 @@ JET.@test_opt
 JET.test_opt
 ```
 
+### [Splitting and filtering reports](@id optanalysis-splitting)
+
+The output of `JET.@report_opt` can be split into individual failures for integration with tools like Cthulhu:
+```@docs
+JET.get_reports
+JET.reportkey
+```
+
 ### [Top-level Entry Points](@id optanalysis-toplevel-entry)
 
 By default, JET doesn't offer top-level entry points for the optimization analysis, because it's usually used for only a

src/JET.jl

@@ -410,6 +410,12 @@ function get_result(result::JETCallResult)
         return result.result.result
     end
 end
+
+"""
+    rpts = JET.get_reports(result::JETCallResult)
+
+Split `result` into a vector of reports, one per issue.
+"""
 function get_reports(result::JETCallResult)
     reports = get_reports(result.analyzer, result.result)
     return configured_reports(reports; result.jetconfigs...)