(#289) Remove black outlines on focus

By default, most browsers place a black outline around the currently-focused element. On mstacm.org, it looks kind of ugly, so some people want it changed. As a quick fix, this commit completely up removes the black outline around focused elements.
People who use Tab to navigate  webpages aren't going to be too happy though, as it's their often only indication of what their cursor is currently on. So I'm hoping we can eventually come up with something else that adds that funcionality back in the future.

apps/web/src/static/css/App.css

@@ -44,4 +44,8 @@ body {
   margin: 0;
   padding: 0;
   font-family: "Nunito Sans", sans-serif;
-}
+}
+
+:focus {
+  outline: none;
+}