Use rem for loading spinner, fix frame bug when loader is scaled up.

src/renderer/components/frame/Frame.css

@@ -58,6 +58,7 @@
 
 /* Windows frame button dock. */
 #frameButtonDockWin {
+    display: flex;
     -webkit-app-region: no-drag !important;
     position: relative;
     top: -2px;
@@ -83,6 +84,7 @@
     height: 22px;
     width: 39px;
     cursor: pointer;
+    line-height: 22px;
 }
 .frameButton:hover,
 .frameButton:focus {

src/renderer/components/loader/Loader.css

@@ -13,6 +13,7 @@
     justify-content: center;
     width: 100%;
     height: calc(100% - 22px);
+    overflow: hidden;
 }
 
 /* Loading content container. */
@@ -35,13 +36,13 @@
 /* Stationary image for the spinner. */
 #loadCenterImage {
     position: absolute;
-    width: 277px;
+    width: 17.3125rem;
     height: auto;
 }
 
 /* Rotating image for the spinner. */
 #loadSpinnerImage {
-    width: 280px;
+    width: 17.5rem;
     height: auto;
     z-index: 400;
 }