fix: fix content width on pages without much content (#1253)

"Solves" misalignment on some pages with too little content.

Before: 


![obrazek](https://github.com/user-attachments/assets/d226837a-288d-4e9e-bf1d-9db4134d5aba)

After: 


https://github.com/user-attachments/assets/264e22f9-b073-4140-ab12-a9324f46ee70

---

The issue persists on mid-size desktop (laptop) screens—the fixed-width
styling can only be applied on large enough displays; otherwise, the
content gets obscured on other pages with actual content.

The moving sidebar is caused by not having enough content (vertically).

Author: barjin

apify-docs-theme/src/theme/custom.css

@@ -445,6 +445,7 @@ html[data-theme="dark"] .DocSearch-Button .DocSearch-Search-Icon {
 .main-wrapper > div {
     max-width: var(--max-layout-width);
     margin: auto;
+    width: 100%;
 }
 
 @media (max-width: 960px) {