fix(styles): remove custom pre padding for highlight.js compatibility

The pre element padding was changed from 1.25rem to zero so that Highlight.js
can control the inner spacing of code blocks through its own theme stylesheet.

With the github theme loaded, Highlight.js applies its own padding to the pre
element via the .hljs class. Keeping the original 1.25rem caused double padding,
making code blocks look oversized compared to the rest of the page.

Author: vidalvasconcelos

public/assets/styles.css

@@ -102,7 +102,7 @@ pre {
     background: #f8f8f8;
     border: 1px solid #e5e5e5;
     border-radius: 6px;
-    padding: 1.25rem;
+    padding: 0;
     overflow-x: auto;
     line-height: 1.5;
     margin: 1.5rem 0;