Examples fail to typecheck with compilerOptions.strict=true in tsconfig

[jyasskin]

Some of the fixes are easy, like adding : Component<{ item: number }> after const Sortable or :DragEventHandler after onDragStart, but some of the others are less convenient, like currentItems.indexOf(draggable.id) failing because Id includes both strings and numbers while currentItems is more precisely typed as just numbers.

[martinpengellyphillips]

I deliberately didn't include typings in the examples because I think it adds unnecessary complexity for folks looking at them (if they are not used to typescript for example).

Maybe when creating fuller documentation adding them in would make sense.