Fixes #24. Adds new configurable option to not shrink wrap list items

[absar]

Fixes #24. Adds new configurable option to not shrink wrap list items using S2ChoiceConfig.shrinkWrap or SmartSelect.single.choiceShrinkWrap/SmartSelect.multiple.choiceShrinkWrap.
If choiceShrinkWrap is true choices list will shrink wrap the choices, causing the list to resize based on the number of available choices, by default it will shrink wrap which was the default behaviour before this change.

Usage:

SmartSelect<T?>.single(
  choiceShrinkWrap: false
);

SmartSelect<T?>.multiple(
  choiceShrinkWrap: false
);

After fix if you pass SmartSelect.single.choiceShrinkWrap=false

SizeIssueFix.mp4

[absar]

@vasilich6107 please merge this