Add test and example to documentation of click / doubleClick with alt/cmd

[rwjblue]

This should be possible as of #398, but we should confirm with a test and then add an exmaple to the API docs.

Tests are here:

ember-test-helpers/tests/unit/dom/click-test.js

Lines 99 to 105 in 8d63527

	test('clicking passes options through to mouse events', async function(assert) {
	element = buildInstrumentedElement('div', ['clientX', 'clientY', 'button']);
	await click(element, { clientX: 13, clientY: 17, button: 2 });
	assert.verifySteps(['mousedown 13 17 2', 'mouseup 13 17 2', 'click 13 17 2']);
	});

Docs are here:

ember-test-helpers/addon-test-support/@ember/test-helpers/dom/click.ts

Lines 26 to 56 in 8d63527

	/**
	Clicks on the specified target.
	Sends a number of events intending to simulate a "real" user clicking on an
	element.
	For non-focusable elements the following events are triggered (in order):
	- `mousedown`
	- `mouseup`
	- `click`
	For focusable (e.g. form control) elements the following events are triggered
	(in order):
	- `mousedown`
	- `focus`
	- `focusin`
	- `mouseup`
	- `click`
	The exact listing of events that are triggered may change over time as needed
	to continue to emulate how actual browsers handle clicking a given element.
	Use the `options` hash to change the parameters of the MouseEvents.
	@public
	@param {string|Element} target the element or selector to click on
	@param {Object} options the options to be merged into the mouse events
	@return {Promise<void>} resolves when settled
	*/

[nummi]

Use the options hash to change the parameters of the MouseEvents.

Maybe more text could be added here to explain that all event properties can be set here (I think that's the case). For example, I needed to test alt clicking a button and it wasn't clear to me that you could simply do this: click(el, { altKey: true }).