[Feature Request] Improve bold text

# Feature Request

## Is your feature request related to a problem? Please describe
I often miss important bold text, which is annoying because bold text is important.

## Describe the solution you'd like
There are two methods, I think, that can make bold text more eye-catching:

1. Increase the text stroke for bold text (or decrease the text stroke for non-bold text)
2. Increase the brightness of bold text (or decrease the brightness of non-bold text)

Some people may want to choose how they brighten or thicken their bold text, so each of these methods might merit a toggle or a slider in the "Font & more" section of the theme customizer—perhaps "Bold text stroke" and "Bold text brightness."

## Additional context

Based on #23, it seems like method 1 has been implemented before (back in 2016), but with some blurriness side-effects. Is it still in use now? I'm aware of the "Text stroke" slider, but that affects all text, not just the bold stuff. Because of the blurriness side-effects, I would prefer to use method 2.