Let the counter chart stack download channels

Following up to #179:

What kind of feature do you want?

Download counts for each channel (Packagist-composer, TER-composer, TER-EM, TER-manual-download) could be stacked upon each other in the chart.

I suggest to use a single bar for each version whereas the portion of each channel gets a different color. Now that the channels are stacked on each other the totals are still visible (overall, that's still the most valuable information).

Now that highcharts supports stacking, it should still be of use.

What are the benefits?

We would see which download channel is used by users.

Alternative

Highcharts also supports line charts (with colored areas) which can be stacked.