[BUG] Indentation rulers in light theme are overly contrasting

[marijnvdwerf]

Describe the bug
When the light theme is selected, the indentation markers are overly high contrasting with the background.

Potential solution:
The indentation markers seem to be a hardcoded colour. Maybe they should be something like color-mix(in srgb, var(--code-foreground), transparent 60%);