Feature/add radiation input

[vgro]

This PR adds top of canopy shortwave downward radiation to the dummy example data. I noticed that this is a required variable when I started testing ve_run with the mechanistic abiotic model. I also noticed that molar density of air and specific heat of air were calculated but not added to the data object, so I updated that. The model is still not running but I stopped here as priorities shifted towards completing the simple abiotic model.

Type of change

• [ ] New feature (non-breaking change which adds functionality)
• [x] Optimization (back-end change that speeds up the code)
• [ ] Bug fix (non-breaking change which fixes an issue)

Key checklist

• [x] Make sure you've run the pre-commit checks: $ pre-commit run -a
• [x] All tests pass: $ poetry run pytest

Further checks

• [x] Code is commented, particularly in hard-to-understand areas
• [x] Tests added that prove fix is effective or that feature works

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 58.82353% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 94.52%. Comparing base (5621b8d) to head (423134d).

Files	Patch %	Lines
...tion_scripts/topofcanopy_radiation_example_data.py	0.00%	7 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #423 +/- ## =========================================== - Coverage 94.69% 94.52% -0.17% =========================================== Files 69 70 +1 Lines 3732 3744 +12 =========================================== + Hits 3534 3539 +5 - Misses 198 205 +7 ```

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