cgit: add line highlighting

hosts/electra/services/cgit/cgit.css

@@ -1,6 +1,10 @@
 td.linenos {
     width: 2em;
+    font-size: 0.9em;
+    padding-top: 1.28em;
 }
+
+/* Highlight diff */
 code span.head {
     color: var(--highlight);
 }
@@ -16,3 +20,19 @@ code span.add {
 code span.del {
     color: var(--negative);
 }
+
+/* Light up targeted line (for linking, etc) */
+pre > code {
+    position: relative;
+}
+pre > code a {
+    height: 1.18rem;
+    width: 101.96%;
+    position: absolute;
+    left: -1em;
+    pointer-events: none;
+}
+pre > code a:target {
+    background-color: var(--highlight);
+    opacity: 0.3;
+}