add GPT detector data

[simonpcouch]

Seeing that same

Writing data_detectors.Rd
Warning message:
[detectors.R:13] @details failed to evaluate inline markdown code
Caused by error in `map_chr()`:
ℹ In index: 1.
Caused by error in `pin_meta()`:
! Can't find pin called "detectors"
ℹ Use `pin_list()` to see all available pins in this board 

...which I think is okay?

[EmilHvitfeldt]

Did you follow the design document on how to add data sets?

You want to, uncommit the NAMESPACE, NEWS.md, R/detectors.R files. And then this PR should be clean. Then once that is merged, you can add the NAMESPACE, NEWS.md, R/detectors.R files in a separate PR 😄

Like how it was done in #27 and #26

[simonpcouch]

Ah, heard! Will make that happen.