Add Light/Dark Mode

[StanFromIreland]

I've added a simple Light/Darkmode toggle. I also capitalized table headings and rounded table corners for aesthetic.
Icons are from Googles open source collection.

Renders

Note: Hardcoded test data was used.

[hugovk]

On first load it looks like this:

I have my OS in dark mode, can we have it autodetect?

Then when I click the icon, the table header text and branch names remain in black. The language text links are also hard to read:

And clicking the icon again, the header and branch names switch to white:

[StanFromIreland]

I will look into why it dosen't work in different browsers as I only tested if Firefox and everything seemed ok.

[m-aciek]

I learned today that the browser/OS preference can be checked with a media query:

@media (prefers-color-scheme: dark) {
  body {background-color: #2f2f2f;}
}

Maybe a first iteration could be without the toggle, just basing on the OS preferences?