fix: update fancy reporter backticks highlighter

[stafyniaksacha]

Resolves #380

This PR ensure only single-line backticks are fancied and that backticks remains to the output.
Also added tests about single-line and multi-line backticks (markdown style).

I'm wondering if we want to color multi-line ? Not sure if it's relevant. We can do so with a regex like:

`([^`\n]+?)`|`{3}([\s\S]*?)`{3}