style(docs): add subtle shadow to screenshots

Signed-off-by: Maksim Sukharev <antreesy.web@gmail.com>

Author: Antreesy

_shared_assets/static/custom.css

@@ -73,6 +73,16 @@ h6 {
 	}
 }
 
+/* Screenshots — add subtle shadow to distinguish from page background */
+.rst-content img {
+	border-radius: 10px;
+	box-shadow: 0 2px 8px rgba(0, 0, 0, 0.15);
+}
+
+html[data-theme="dark"] .rst-content img {
+	box-shadow: 0 2px 8px rgba(255, 255, 255, 0.15);
+}
+
 /* ICONS LIST */
 div#list-of-available-icons > blockquote {
 	margin: 0;