feat: Add gaze.transforms.smooth()

[jakobchwastek]

Description

Fixes issue #301

Implemented changes

Implementation of transforms.smooth function for smoothing data. The following methods have been implemented

• Moving Average
• Exponential Moving Average
• Savitzky Golay

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

Tested smoothing methods by applying them to a simple 2D array with values [[0., 0.], [1., 1.], [0., 0.]].

Checklist:

• [ ] My code follows the style guidelines of this project
• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have made corresponding changes to the documentation
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] Any dependent changes have been merged and published in downstream modules
• [ ] I have checked my code and corrected any misspellings

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (c8ef04d) 100.00% compared to head (67bbbde) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #555 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 52 52 Lines 2258 2289 +31 Branches 559 570 +11 ========================================= + Hits 2258 2289 +31 ``` | [Files](https://app.codecov.io/gh/aeye-lab/pymovements/pull/555?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aeye-lab) | Coverage Δ | | |---|---|---| | [src/pymovements/gaze/gaze\_dataframe.py](https://app.codecov.io/gh/aeye-lab/pymovements/pull/555?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aeye-lab#diff-c3JjL3B5bW92ZW1lbnRzL2dhemUvZ2F6ZV9kYXRhZnJhbWUucHk=) | `100.00% <100.00%> (ø)` | | | [src/pymovements/gaze/transforms.py](https://app.codecov.io/gh/aeye-lab/pymovements/pull/555?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=aeye-lab#diff-c3JjL3B5bW92ZW1lbnRzL2dhemUvdHJhbnNmb3Jtcy5weQ==) | `100.00% <100.00%> (ø)` | |

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[jakobchwastek]

Adding smooth as transformation method in GazeDataFrame is missing!