0.5.0 - preset themes and style defaults

Preset themes

A diagram can pick one of thirteen with diagram theme: solarized-light (light, dark, Solarized, Gruvbox, Catppuccin, Nord, Dracula, high contrast, print), and reladraw --theme <name> renders a file in another theme without editing it. The playground has a theme picker.

Style defaults

default node | leaf | container | edge sets what every thing of that kind looks like unless it says otherwise, and diagram text: (color: …) sets every text's color at once.