slightly improve style

core/static/core/style.scss

@@ -19,6 +19,13 @@ body {
   --loading-stroke: 5px;
   --loading-duration: 1s;
   position: relative;
+
+  &.aria-busy-grow {
+    // Make sure the element take enough place to hold the loading wheel
+    min-height: calc((var(--loading-size)) * 1.5);
+    min-width: calc((var(--loading-size)) * 1.5);
+    overflow: hidden;
+  }
 }
 
 [aria-busy]:after {
@@ -255,6 +262,13 @@ body {
     }
   }
 
+  /**
+  * A spacer below an element. Somewhat cleaner than putting <br/> everywhere.
+  */
+  .margin-bottom {
+    margin-bottom: 1.5rem;
+  }
+
   /*--------------------------------CONTENT------------------------------*/
   #quick_notif {
     width: 100%;