[redesign] implement dark mode

[neb-b]

This will include cleaning up all the color variables/removing what we don't need

[btzr-io]

@seanyesmunt Do you need any help with this ?
I'm currently fixing the dark theme on redesign just to see how will look 👀

BTW redesign is looking awesome 👍

[neb-b]

Yeah if you are interested I would love some help with this! Colors across the redesign branch are missing a lot of stuff. I was planning on working on this last so feel free to make a PR to redesign if you would like!

You can check out http://lbry.zzk.fr/explore to get an idea of the new dark mode colors.

[neb-b]

@btzr-io I think currently there are a fair bit of color variables that aren't being used. Feel free to delete those/rename any that are confusing.

I know I've used color variables instead of a specific element variables as I've been working on this just to save some time. Ex:

.btn {
  background-color: var(--color-primary);
}

which should be something like

.btn {
  background-color: var(--button-background);
}

Same for color: var(--color-black) instead of color: var(--text-color)

Let me know if you have any questions!