* DataTable sort by function (or other callable)
The `DataTable` widget now takes the `by` argument instead of `columns`, allowing the table to also be sorted using a custom function (or other callable). This is a breaking change since it requires all calls to the `sort` method to include an iterable of key(s) (or a singular function/callable). Covers #2261 using [suggested function signature](https://github.com/Textualize/textual/pull/2512#issuecomment-1580277771) from @darrenburns on PR #2512.
* argument change and functionaloty update
Changed back to orinal `columns` argument and added a new `key` argument
which takes a function (or other callable). This allows the PR to NOT BE
a breaking change.
* better example for docs
- Updated the example file for the docs to better show the functionality
of the change (especially when using `columns` and `key` together).
- Added one new tests to cover a similar situation to the example
changes
* removed unecessary code from example
- the sort by clicked column function was bloat in my opinion
* requested changes
* simplify method and terminology
* combine key_wrapper and default sort
* Removing some tests from DataTable.sort as duplicates. Ensure there is test coverage of the case where a key, but no columns, is passed to DataTable.sort.
* Remove unused import
* Fix merge issues in CHANGELOG, update DataTable sort-by-key changelog PR link
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Co-authored-by: Darren Burns <darrenburns@users.noreply.github.com>
Co-authored-by: Darren Burns <darrenb900@gmail.com>
