Add method priceLines in ISeriesAPI

[signatenkov]

Type of PR: enchantment
PR checklist:

• Closes: Feature: Get priceLines from ISeriesAPI #1532

Overview of change:

Adds new method priceLines() to ISeriesApi interface

[SlicedSilver]

Could we rather create a new test case?

You can use this test-case as a starting point, and then instead of removing the price lines rather use the returned IPriceLine to modify the existing price lines so there is a visual difference on the chart.

return new Promise(resolve => {
	setTimeout(() => {
		const [line1, line2] = series.priceLines();
		series.removePriceLine(line1); // still check it can be removed
		line2.applyOptions({
			price: 15,
			color: 'red',
		});
		resolve();
	}, 1000);
});

Additionally, it might be good to check that the array is a copy and if modified then it won't break anything:

// create 3 price lines...
return new Promise(resolve => {
	setTimeout(() => {
		const priceLines = series.priceLines();
		const [line1, line2, line3] = priceLines;

		priceLines.splice(2,1); // remove line 3 from array, however line3 should still be visible on the chart

		series.removePriceLine(); // still check it can be removed
		line2.applyOptions({
			price: 15,
			color: 'red',
		});
		resolve();
	}, 1000);
});

[signatenkov]

#1739