Add tests for using the browser window's selection as the default search query

[krassowski]

We need to add an integration test for the improvements added by #15834

The current test is defined here:

jupyterlab/galata/test/jupyterlab/notebook-search.test.ts

Lines 104 to 152 in d582282

	test('Populate search box with selected text', async ({ page }) => {
	// Enter first cell
	await page.notebook.enterCellEditingMode(0);
	// Go to first line
	await page.keyboard.press('PageUp');
	// Select first line
	await page.keyboard.press('Shift+End');
	// Open search box
	await page.keyboard.press('Control+f');
	// Expect it to be populated with the first line
	const inputWithFirstLine = page.locator(
	'[placeholder="Find"] >> text="Test with one notebook withr"'
	);
	await expect(inputWithFirstLine).toBeVisible();
	await expect(inputWithFirstLine).toBeFocused();
	// Expect the newly set text to be selected
	expect(await inputWithFirstLine.evaluate(getSelectionRange)).toStrictEqual({
	start: 0,
	end: 28
	});
	// Expect the first match to be highlighted
	await page.waitForSelector('text=1/2');
	// Enter first cell again
	await page.notebook.enterCellEditingMode(0);
	// Go to last line
	await page.keyboard.press('PageDown');
	// Select last line
	await page.keyboard.press('Shift+Home');
	// Update search box
	await page.keyboard.press('Control+f');
	// Expect it to be populated with the last line
	const inputWithLastLine = page.locator(
	'[placeholder="Find"] >> text="This is a multi line with hits with"'
	);
	await expect(inputWithLastLine).toBeVisible();
	await expect(inputWithLastLine).toBeFocused();
	// Expect the newly set text to be selected
	expect(await inputWithLastLine.evaluate(getSelectionRange)).toStrictEqual({
	start: 0,
	end: 35
	});
	await expect(page.locator('.jp-DocumentSearch-overlay')).toBeVisible();
	});