fix: Common substring() Pitfalls

Author: danieldanielecki

data/blog/software-development/web-development/frontend/javascript/slice-vs-substring-vs-substr-complete-javascript-string-methods-comparison.mdx

@@ -654,7 +654,7 @@ console.log(str.slice(-4, 10));         // "ript" (from index -4 which is positi
 // slice() correctly interprets negative start (6), substring() treats negative start as 0
 ```
 
-#### Common substring() Pitfalls
+#### Common `substring()` Pitfalls
 
 ```javascript
 // Pitfall 1: Assuming negative indices work like slice()