Tom/adding tests

[thomasarmstrong98]

Pull Request

Description

Addressing #5 and #6

Add basic test coverage for preprocessing and utility functions. Also converts .npy data to pd.DataFrame storage for processed NWP data (better inclusion of the timepoints at which the data corresponds to)

Stores a test/sample nwp sample used for testing.

How Has This Been Tested?

All tests passed successfully

• [X ] Yes

Checklist:

• [X ] My code follows OCF's coding style guidelines
• [ X] I have performed a self-review of my own code
• [ X] I have made corresponding changes to the documentation
• [ X] I have added tests that prove my fix is effective or that my feature works
• [ X] I have checked my code and corrected any misspellings

[thomasarmstrong98]

Would you be able to add CI to this PR too

Doesn't that require the setup.py and requirements.txt first? @peterdudfield