Make out-of-the-box usable default config

[nekitk]

It would be helpful to have a default config which is reaty-to-use. For that it should include:

• basic colors — it should be minimal yet sufficient to style a regular web app
• color descriptions — when to use each color, how they are related (e.g., secondary + hover = default)
• shadows
• dark theme (either as a separate config, or as an easilty deletable part of the default config)
• fonts — font families with fallbacks, sizes and line heights
• spaces