Support boolean as a11y type

[farseekers]

The a11y documentation says that it accepts a boolean,

https://swiperjs.com/swiper-api#param-a11y

Object with a11y parameters or boolean true to enable with default settings.

but the type definition does not support this.

swiper/src/types/swiper-options.d.ts

Line 895 in 3a1777a

a11y?: A11yOptions;

This PR adds it, mirroring the behaviour of autoplay

swiper/src/types/swiper-options.d.ts

Lines 898 to 909 in 3a1777a

	* Object with autoplay parameters or boolean `true` to enable with default settings
	*
	* @example
	* ```js
	* const swiper = new Swiper('.swiper', {
	* autoplay: {
	* delay: 5000,
	* },
	*});
	* ```
	*/
	autoplay?: AutoplayOptions | boolean;