title: Trouble with x-axis labels in ngx-charts
body: <p>I'm working with ngx-charts to display data in a line-charts.
  The problem is in labels: in some cases the data is scrambled and the sort is wrong. Here's an example here:</p>
  <p>example wrong labels order</p>
  <p><img src="https://i.stack.imgur.com/vRzSO.png" alt="1" /></p>
  <p>Now, I tried many many ways to sort them. The label are strings coming from data objects, so first thing that I tried is sorting the data, and then generating the string labels, but it's not working. Then I tried to use label directly as date object e formatted them with [xAxisTickFormatting] property of the chart component: not only the labels were formatted in the wrong way, but apparently with this method i was unable to control the number of them (for instance, in the previous example I show week ranges. Using labels directly as Date object make the ngx-charts showing only day-of-months, no matter what).</p>
  <p>Any suggestion to solve this?</p>