Enable Stylelint rules for vendor prefixes

This commit also removes a bunch of vendor prefixes that were in the styles
but are no longer needed since PostCSS and Autoprefixer handles generating
them.

src/index.html

@@ -126,16 +126,6 @@
             left: 0;
         }
 
-        @-webkit-keyframes fadein {
-            from {
-                opacity: 0;
-            }
-
-            to {
-                opacity: 1;
-            }
-        }
-
         @keyframes fadein {
             from {
                 opacity: 0;
@@ -147,7 +137,6 @@
         }
 
         .splashLogo {
-            -webkit-animation: fadein 0.5s;
             animation: fadein 0.5s;
             width: 30%;
             height: 30%;
@@ -158,7 +147,6 @@
             position: fixed;
             top: 50%;
             left: 50%;
-            -webkit-transform: translate(-50%, -50%);
             transform: translate(-50%, -50%);
         }