✨ Support Multiple Special Items

[yujune]

✨ What's the context?

Current AssetPickerConfig only accept single specialItemPosition and specialItemBuilder which is is not suitable for cases where multiple special items is required.

🛠 Changes being made

• Added specialItems in AssetPickerConfig and which accept list of specialItemPosition and specialItemBuilder.
• Added isPermissionLimited param to SpecialItemBuilder typedef for case where special item is required to remove when isPermissionLimited is false. Example as below.

SpecialItem(
                itemPosition: SpecialItemPosition.append,
                itemBuilder: (
                  BuildContext context,
                  AssetPathEntity? path,
                  int length,
                  bool isPermissionLimited,
                ) {
                  if (!isPermissionLimited) {
                    return null;
                  }
                  return const Center(
                    child: Text('Append Widget', textAlign: TextAlign.center),
                  );
                },
              ),

• Removed unused SpecialPosition.none enum.

✨ Result