Sliding broken when slide content is wrapped in anchor tag

I believe this comes from here:

> `img` elements and `a` elements with an `href` attribute have their `draggable` attribute set to true by default.

[HTML spec - Drag and drop](https://html.spec.whatwg.org/multipage/dnd.html#drag-and-drop-processing-model)

Here's the code I think is related to this, with the proposed solution:

```diff
export const swipeStart = (e, swipe, draggable) => {
e.target.tagName === "IMG" && e.preventDefault();

+ // my proposed solution
+ e.target.tagName === "A" && e.preventDefault();

if (!swipe || (!draggable && e.type.indexOf("mouse") !== -1)) return "";
return {
dragging: true,
touchObject: {
startX: e.touches ? e.touches[0].pageX : e.clientX,
startY: e.touches ? e.touches[0].pageY : e.clientY,
curX: e.touches ? e.touches[0].pageX : e.clientX,
curY: e.touches ? e.touches[0].pageY : e.clientY
}
};
};
```

[source](https://github.com/akiran/react-slick/blob/master/src/utils/innerSliderUtils.js#L307)