Fixes #11193: Add kbd element styles to indicate user input via keyboard

less/code.less

@@ -21,6 +21,16 @@ code {
   border-radius: @border-radius-base;
 }
 
+// User input typically entered via keyboard
+kbd {
+  padding: 2px 4px;
+  font-size: 90%;
+  color: @kbd-color;
+  background-color: @kbd-bg;
+  border-radius: @border-radius-small;
+  box-shadow: inset 0 -1px 0 rgba(0,0,0,.25);
+}
+
 // Blocks of code
 pre {
   display: block;

less/variables.less

@@ -602,6 +602,9 @@
 @code-color:                  #c7254e;
 @code-bg:                     #f9f2f4;
 
+@kbd-color:                   #fff;
+@kbd-bg:                      #333;
+
 @pre-bg:                      #f5f5f5;
 @pre-color:                   @gray-dark;
 @pre-border-color:            #ccc;