message: types(Picker): support generic
diff: import { VanComponent } from './component';
  export class Picker extends VanComponent {
  - getValues(): string[];
  + getValues<T = string>(): T[];
  - setValues(values: string[]): void;
  + setValues<T = string>(values: T[]): void;
  getIndexes(): number[];
  setIndexes(indexes: number[]): void;
  - getColumnValue(columnIndex: number): string;
  + getColumnValue<T = string>(columnIndex: number): T;
  - setColumnValue(columnIndex: number, value: string): void;
  + setColumnValue<T = string>(columnIndex: number, value: T): void;
  getColumnIndex(columnIndex: number): number;
  setColumnIndex(columnIndex: number, optionIndex: number): void;
  - getColumnValues(columnIndex: number): string[];
  + getColumnValues<T = string>(columnIndex: number): T[];
  - setColumnValues(columnIndex: number, values: string[]): void;
  + setColumnValues<T = string>(columnIndex: number, values: T[]): void;
  confirm(): void;
  }
  