Added conftest.jl by Porting From Stingray (Python)

[JawadAhmadCS]

Summary

• Added src/conftest.jl to configure testing setup.
• Updated test/runtests.jl to include conftest.jl.
• Now, all tests will run properly.

Changes

• Created conftest.jl
• Updated runtests.jl to load conftest.jl before running tests

Testing

• Run include("test/runtests.jl") in Julia REPL to verify everything is working correctly.
  

This contribution is part of my efforts for Google Summer of Code (GSoC) 2025 to work on Spectral Timing in Julia. Contributing to Stingray.jl helps me gain codebase familiarity and deepen my understanding for meaningful GSoC contributions.

[JawadAhmadCS]

Hey @matteobachetti ! I've added conftest.jl to streamline the testing process for Stingray.jl and updated runtests.jl accordingly. Now, all tests will automatically include version logging and proper test setup. Would love your feedback and suggestions! Let me know if anything needs improvement. Excited to contribute to this awesome project!