Fix line numbers hiding code in fancy-code block styling

[Febulix]

In “fancy-code” blocks, the first two characters of code were being hidden behind the line numbers.

This small update ensures all code is fully visible and accommodates three-digit line numbers.

The fix modifies only two lines:
width of the line-number pseudo-element ::before increased from 1.7em → 2.1em
padding-left of code lines changed from 2.8em → 2.6em !important
The use of !important on padding-left ensures it overrides other theme styles and reliably prevents the overlap.

[Febulix]

Oh, sorry! I didn’t notice bug report #186 or the fix in #187 by @moziar when I submitted my pull request. 🙈
I prefer the solution in #187, but it would be great to keep the spacing changes so that line numbers can go up to three digits.