Show border while input is focused

This won't work on a lot of browsers, but temporarily just target modern ones. (Robust solution is possible using classNames and refs)

src/components/filter/filter.css

@@ -20,6 +20,10 @@
     margin: 0 .5rem;
 }
 
+.filter:focus-within {
+    box-shadow: 0 0 0 .25rem $motion-transparent;
+}
+
 /*
     Hidden state
 */