Main ui (#214)

* Class for file drop

* OCD

* We don't need the invalid state, as we'll accept all types.

* Flattening CSS

* Fixing zoom input in Firefox

* Fixing 'container' scaleTo

* two-up closer design match & smaller line

* Fixing edge bug

src/lib/util.scss

@@ -5,6 +5,7 @@
   width: 100%;
   height: 100%;
   box-sizing: border-box;
+  contain: strict;
 }
 
 .unbutton {