Support parallel execution please!

[skipkent]

LOVE your report, but it only seems to work for single threaded runs. We use pytest-xdist to run on multiple threads, but pytest-html-reporter only reports on one thread.

We have since switched to https://pypi.org/project/pytest-html/ which is not as visually rich as yours but supports multi threaded runs out of the box.

If you have any workarounds or suggestions please let us know, thanks!