docs: add missing column argument docs and note on csv column dtypes

[jakobchwastek]

In this pull request, I've extended the documentation to include previously undocumented arguments in the DatasetDefinition class. The newly documented arguments are:

trial_columns: list[str] | None = None
time_column: str | None = None
pixel_columns: list[str] | None = None
position_columns: list[str] | None = None
velocity_columns: list[str] | None = None
acceleration_columns: list[str] | None = None

Furthermore I added a description to better understand the custom_read_kwargs argument and to which function it will be passed.

As you know I also encountered issues with polars.read_csv inferring wrong data types, leading to failures in the pos2vel transformation. To assist users who might face similar problems I included a note in the documentation.

Let me know if any further refinements are needed.

[codecov[bot]]

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