fix(ui): add non-versioned fontawesome

The current css specifies "FontAwesome 5 Free Solid", for .drawing and
.text-button. This results in the button icons/fonts not rendering
correctly on systems that do not have that exact version of
FontAwesome. This change adds the more generic "FontAwesome" as an
option allowing the icons/fonts to be rendered correctly on these
systems.

res/style/swappy.css

@@ -1,5 +1,5 @@
 .drawing .text-button {
-  font-family: "FontAwesome 5 Free Solid";
+  font-family: "FontAwesome 5 Free Solid", "FontAwesome";
   padding: 4px;
 }