Add open to expose yojson functions used in derives

[mt-caret]

Fixes #200.

I tried running some tests as best as I can but I'm not sure if the test failures I'm getting are relevant to #200.

[akabe]

@mt-caret
First and foremost, let me express our gratitude for your donation. It means a lot to me and keeps me motivated to continue our work.

Also, I wanted to say a thank you for helping me fix the problem that I had left untouched for years.
Your patch looks good, but an integration test related to ppx_yojson_conv fails:

2023-08-09T08:39:07 [INFO] SEND: HMAC=d07f878740bfba2dcea2c2a4dc741c3eaafd5358e3883bcc6a4682def75c80e2; header={"msg_id":"3e80dbb2-de6d-4ca0-a909-530860a8eb3e","msg_type":"error","session":"6f36d72f-bf78e6d077b8440405e80146","date":"2023-08-09T08:39:07.8911Z","username":"runner","version":"5.3"}; parent={"msg_id":"6f36d72f-bf78e6d077b8440405e80146_27949_2","msg_type":"execute_request","session":"6f36d72f-bf78e6d077b8440405e80146","date":"2023-08-09T08:39:07.770278Z","username":"runner","version":"5.3"}; content={"ename":"error","evalue":"compile_error","traceback":["File \"[1]\", line 3, characters 17-20:\n3 | type t = { foo : int; baz : string; } [@@deriving yojson]\n                     ^^^\nError: Unbound value int_of_yojson\n"]}; metadata={}

cf. https://github.com/akabe/ocaml-jupyter/actions/runs/5795450506/job/15740046501?pr=201#step:13:213

Could you add open Ppx_yojson_conv_lib.Yojson_conv.Primitives to the file tests/integration/ppx.ipynb?

[mt-caret]

First and foremost, let me express our gratitude for your donation. It means a lot to me and keeps me motivated to continue our work.

Thank you for working on this amazing project; I'm impressed by how well this works, and sponsoring your work is the very least I can do :)

Could you add open Ppx_yojson_conv_lib.Yojson_conv.Primitives to the file tests/integration/ppx.ipynb?

Done!

[akabe]

Thank you so much!

[akabe]

@mt-caret
In case you're interested, I have the option to add your icon and a web page link to the README#Sponsors. Please let me know your thoughts on how you'd like to proceed.

[mt-caret]

Thanks so much for the offer, but no thanks; my sponsorships are all private, and I'm not very interested in advertising my sponsorships :)