Add API type to public API

[tkf]

While using PublicAPI outside, I noticed that not being able to dispatch on the API type is a pain tkf/DocumentationOverview.jl#5 (comment)

So, I suggest exposing the type API. I hide the constructor for now just in case we want to change the signature.

[codecov]

Codecov Report

Merging #14 (cb61b46) into main (ef5d7d7) will not change coverage.
The diff coverage is 83.33%.

@@           Coverage Diff           @@
##             main      #14   +/-   ##
=======================================
  Coverage   93.51%   93.51%           
=======================================
  Files           4        4           
  Lines         108      108           
=======================================
  Hits          101      101           
  Misses          7        7           

Flag	Coverage Δ
unittests	93.51% <83.33%> (ø)

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Impacted Files	Coverage Δ
src/query.jl	87.87% <80.00%> (-0.36%)	⬇️
src/PublicAPI.jl	100.00% <100.00%> (ø)

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