Allow defaults for list-item DropIndicator Instruction

[joshkel]

The new list-item DropIndicator is (I assume) designed to get its instructions from the list-item hitbox, which provides a complete Instruction object. However, the Instruction type makes it more awkward to use directly (apart from the hitbox):

export type Instruction = {
    [TOperation in Operation]: {
        operation: TOperation;
        blocked: boolean;
        axis: Axis;
    };
}[Operation];

return <DropIndicator instruction={{ type: 'combine', axis: 'vertical', blocked: false }} />;

Could the types be relaxed to provide more defaults?

export type Instruction = {
    [TOperation in Operation]: {
        operation: TOperation;
        blocked?: boolean; // defaults to false
        axis?: Axis; // defaults to 'vertical', just like hitbox
    };
}[Operation];

return <DropIndicator instruction={{ type: 'combine' }} />;