Please provide a way to inject custom css into the report

[BillyTom]

Is your feature request related to a problem? Please describe.
Usability problem: Our test cases have very long descriptions, but the nav bar on the left side of the report is only 320 pixels wide. The result is that most of the test descriptions in the nav bar are cut off, even though there is still a lot of screen space available.

Describe the solution you'd like
I would like to change a few styles in the report, e.g. Increase the width of the nav-bar, or make some section headers bold.

Describe alternatives you've considered
I have tried to directly change the styles in dist/app.css and then create a yarn patch. This solution has several drawbacks: Since app.css is all squished together, even changing one single pixel value will result in a huge diff file. This will be hard to maintain in the long run.