CSS: Add .controls class with box-shadow and layout properties

public/css/common.less

@@ -27,6 +27,21 @@ pre {
   border-radius: initial;
 }
 
+.controls {
+  // Copied from Icinga DB Web
+  -moz-box-shadow: 0 0 0 1px var(--gray-lighter, #4b4b4b);
+  -webkit-box-shadow: 0 0 0 1px var(--gray-lighter, #4b4b4b);
+  box-shadow: 0 0 0 1px var(--gray-lighter, #4b4b4b);
+  flex-shrink: 0; // Prevents shrinking in a flex container
+  position: relative;  // Positions the element relative to its normal position
+  z-index: 1; // Ensures the element stacks above others
+
+  footer {
+    height: 1em;
+  }
+}
+
+
 .horizontal-key-value,
 .vertical-key-value {
   > .value {