Add unit support

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 97.50000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 94.73%. Comparing base (ac7a6b0) to head (6a55fc5).

Files	Patch %	Lines
src/conversion.jl	83.33%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #85 +/- ## ========================================== - Coverage 94.85% 94.73% -0.12% ========================================== Files 17 17 Lines 1068 1063 -5 ========================================== - Hits 1013 1007 -6 - Misses 55 56 +1 ```

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