Aliki: Add padding to TOC (#1481)

I'm unsure if rdoc uses this somewhere but here is how it looks like on
https://docs.ruby-lang.org/en/master/String.html

<img width="348" height="637" alt="image"
src="https://github.com/user-attachments/assets/c60cd491-1dee-448e-b2eb-01cd85c5c6ed"
/>

In #1479 I wrote about it not being
formatted. Since the TOC is generated via javascript, that seems a bit
difficult to fix.

But I'm unsure if that is even needed. What was bothering me was that
there was no connection between the "What's Here" and its subsections.
This fixes that in a pretty simple way.

Co-authored-by: Stan Lo <stan001212@gmail.com>

Author: Earlopain

lib/rdoc/generator/template/aliki/css/rdoc.css

@@ -1318,6 +1318,14 @@ aside.table-of-contents .toc-sticky nav {
   height: auto;
 }
 
+aside.table-of-contents .toc-list > .toc-h2 {
+  margin-left: var(--space-4);
+}
+
+aside.table-of-contents .toc-list > .toc-h3 {
+  margin-left: var(--space-8);
+}
+
 /* Hide TOC on mobile/tablet */
 @media (width <= 1279px) {
   aside.table-of-contents {