This adds back the `dropdownAutoWidth` option, so the dropdown can
have a width that is automatically determined by the browser. This
works best for smaller dropdowns that contain options with large
amounts of text.
This closes https://github.com/select2/select2/issues/3103.
This closes https://github.com/select2/select2/pull/3113.
Signed-off-by: Kevin Brown <kevin@kevin-brown.com>
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