Add hover callback for LinkProviders

[Coding-Kiwi]

The LinkMatchers are eventually removed, right?
If you pass _useLinkProvider to the xterm-web-links-addon, there is currently no way to get a hover callback to show a tooltip.
I would like to switch to the LinkProvider but I also want to show a tooltip when hovering a link

[Tyriar]

👍 PR welcome to add the hover callback to the web link provider, it needs to get added to the result ILinks:

xterm.js/typings/xterm.d.ts

Lines 1146 to 1153 in 566fad4

	/**
	* Called when the mouse hovers the link. To use this to create a DOM-based hover tooltip,
	* create the hover element within `Terminal.element` and add the `xterm-hover` class to it,
	* that will cause mouse events to not fall through and activate other links.
	* @param event The mouse event triggering the callback.
	* @param text The text of the link.
	*/
	hover?(event: MouseEvent, text: string): void;

[Coding-Kiwi]

@Tyriar this would be a quick and dirty way of passing the callbacks through, what do you think

https://github.com/Coding-Kiwi/xterm.js/commit/8d7958c3df3b6a00a3623cf591ae67e186507711

[Tyriar]

@Coding-Kiwi something like that is what I was thinking, decorating the result of computeLinks in a separate function would be preferable though:

const links = LinkComputer.computeLink(y, this._regex, this._terminal, this._handler);
callback(addCallbacks(links, this._options.tooltipCallback, this._options.leaveCallback);

Want to iterate on it in a PR?