font size in the nebula book

[wey-gu]

The font size is smaller than averages ones, it's actually quite read-friendly on the big screen in zoomed scale, while, in some other cases, i.e. some reading devices, it's too small.

Could we enlarge the font size?(Aha, I know it will end up with many more pages)

Thanks!

context:

• One of our contributor mentioned this to me today :-)

[whitewum]

You are welcome to generate a specific version for him. All texts and tools are based on open source. tips: try mkdoc.yml.

But the default font is designed for 4k screen for the majority of uses.

[wey-gu]

cc @hezhizhen