feat: Animated 404 image, some style improvements, more attributions

sass/_main.scss

@@ -114,6 +114,7 @@ strong {
 
 small {
   color: var(--fg50);
+  font-size: 0.8rem;
 }
 
 dl {
@@ -162,6 +163,7 @@ blockquote > blockquote {
 
 abbr {
   cursor: help;
+  text-decoration: underline dotted;
 }
 
 kbd {
@@ -255,7 +257,7 @@ figcaption {
   display: block;
   text-align: center;
   color: var(--fg50);
-  font-size: 0.9rem;
+  font-size: 0.8rem;
 }
 
 details {
@@ -277,7 +279,7 @@ table {
   max-width: 100vw;
   overflow: auto;
   word-break: normal;
-  word-break: keep-all; // For Firefox to horizontally scroll wider tables.
+  word-break: keep-all; // for Firefox to horizontally scroll wider tables.
   -webkit-overflow-scrolling: touch;
 }