CONTRIBUTING: mark C code properly (#36806)

This makes the section way more readable.

Author: zlatanvasovic

CONTRIBUTING.md

@@ -266,11 +266,11 @@ runtest harness).
 #### General Formatting Guidelines For C code contributions
 
  - 4 spaces per indentation level, no tabs
- - space between if and ( (if (x) ...)
- - newline before opening { in function definitions
- - f(void) for 0-argument function declarations
- - newline between } and else instead of } else {
- - if one part of an if..else chain uses { } then all should
+ - space between `if` and `(` (`if (x) ...`)
+ - newline before opening `{` in function definitions
+ - `f(void)` for 0-argument function declarations
+ - newline between `}` and `else` instead of `} else {`
+ - if one part of an `if..else` chain uses `{ }` then all should
  - no whitespace at the end of a line
 
 ### Git Recommendations For Pull Requests