Rework colors variables to use primary/secondary and make them configurable

[alimtunc]

I've added the simplest way I found to have custom CSS color on lemverse, but firstly I've replaced some SCSS color variables to be generic using primary and secondary keyword.

Now, we need to just need to update primary and secondary color on settings.json

[alimtunc]

Okay, all good for a review, color customization is now on settings.json 🙌 @Donorhan

[ramnes]

@Donorhan Is there anything we can do? :)

[Donorhan]

I'm not entirely comfortable with this integration. Going through JS and CSS variables seems a bit overkill to me and at the same time I haven't found any other solutions yet 😅

I did think about having a file that overloads the variables file at the build but the Meteor build seems a bit limited for that.

[ramnes]

Why does it seem overkill to you? That's how we achieved #158 as well so both PR are quite consistent.

The settings are read at runtime so if we want to keep all the configuration stuff there, we have to work at runtime as well and there isn't many ways.

Also, settings at runtime could end up being super useful if we want to make the UI theme editable on the level side later. :)