Add object type support

[mzp]

Some type definition of major library(e.g. lodash, jQuery) use extends object.

at<T extends object>(
            object: T | null | undefined,
            ...props: Array<Many<keyof T>>
        ): Array<T[keyof T]>;

Because current scala-js-ts-importer converts object to object, converted file is not compilable.

📝 Example

Source

declare interface LoDashStatic {
  at<T extends object>();
};

Current

trait LoDashStatic extends js.Object {
  def at[T <: `object`](): js.Dynamic = js.native
}

After merging this pull request

trait LoDashStatic extends js.Object {
  def at[T <: js.Object](): js.Dynamic = js.native
}