Fix social-links margins being zeroed by the global ul[class] reset

The reset rule (body, h1, ..., ul[class], ol[class], ..., dd { margin:
0 }) matches via ul[class] at specificity (0,0,1,1), which beats plain
class selectors like .social-links/.social-links--large (0,0,1,0)
regardless of source order - so the margin-top values set for both the
sidebar gap and the About-me divider-to-icon gap were silently always
overridden back to 0. Prefixing both selectors with the ul type
selector ties the specificity, letting these (later in the file) win.

static/css/site.css

@@ -386,7 +386,13 @@ ul.menuitems {
   content: "Translations: ";
 }
 
-.social-links {
+/* "ul.social-links", not ".social-links": the global reset rule
+   (body, h1, ..., ul[class], ol[class], ..., dd { margin: 0; }) matches
+   via ul[class] at specificity (0,0,1,1), which beats a plain single-class
+   selector like ".social-links" (0,0,1,0) regardless of source order.
+   Adding the "ul" type selector ties it at (0,0,1,1), so this rule (being
+   later in the file) wins instead of always being zeroed back out. */
+ul.social-links {
   display: flex;
   flex-wrap: wrap;
   justify-content: center;
@@ -422,8 +428,9 @@ ul.menuitems {
 
 /* About-me page variant: bigger icons, distinct gap from the text above.
    Spacing to the preceding text is handled by .social-links-divider's
-   own margins, so this only needs the gap from divider to icons. */
-.social-links--large {
+   own margins, so this only needs the gap from divider to icons.
+   "ul.social-links--large" for the same specificity reason as above. */
+ul.social-links--large {
   margin-top: 3rem;
   gap: 1.5rem;
 }