Implementing rolling median function for metrics.py

[frey-perez]

• resolves #30

This function implements the rolling median function, a function meant to pre-process acceleration data before determining angle_relative_to_horizontal values. All relevant unit tests are included.

[codecov[bot]]

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```diff @@ Coverage Diff @@ ## development #38 +/- ## ============================================= Coverage 100.00% 100.00% ============================================= Files 4 4 Lines 113 120 +7 ============================================= + Hits 113 120 +7 ```

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[nx10]

Why not use https://docs.pola.rs/py-polars/html/reference/expressions/api/polars.Expr.rolling_median.html and other polars.rolling_* methods instead of implementing all of these?

• https://github.com/childmindresearch/wristpy/pull/31
• https://github.com/childmindresearch/wristpy/pull/34
• https://github.com/childmindresearch/wristpy/pull/38

[ReinderVosDeWael]

Why not use https://docs.pola.rs/py-polars/html/reference/expressions/api/polars.Expr.rolling_median.html and other polars.rolling_* methods instead of implementing all of these?

• Implementing moving_mean function in metrics.py #31
• Adding moving_std to computations #34
• Implementing rolling median function for metrics.py #38

Fair point - for now, as there's some design questions to be answered regarding handling of even window size and unit of window size, lets leave this for now. I'll make an issue out of it though so we can reassess this when those issues are resolved.