Use monospace font stack

Bootstrap 4 has a monospace font stack which is nicer than the generic `monospace` family name.
It will select the system fonts by default, and then fall back to `monospace`.
Using system fonts is a good practice, also GitHub uses a similar font stack in their CSS.
The font stack is defined here: https://github.com/twbs/bootstrap/blob/v4.1.3/scss/_variables.scss#L252

Author: sebdesign

src/Report/Html/Renderer/Template/css/style.css

@@ -64,7 +64,7 @@ td.small {
 }
 
 td.codeLine {
- font-family: monospace;
+ font-family: "SFMono-Regular", Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  white-space: pre;
 }