add kbd style

res/css/app.less

@@ -73,3 +73,4 @@
 @import "components/search";
 @import "components/chart";
 @import "components/claim";
+@import "components/keystroke";

res/css/components/base.less

@@ -160,6 +160,10 @@ pre {
     color: @color-primary;
 }
 
+kbd {
+    font-family: 'Roboto Mono', monospace;
+}
+
 // force all inputs on iOS devices to a font-size of 16px,
 // because otherwise iOS will zoom into the input fields on-focus
 @media screen and (pointer: coarse) and (-webkit-min-device-pixel-ratio: 0) {

res/css/components/keystroke.less

+.keystroke {
+    background-color: #f7f7f7;
+    border: 1px solid #ccc;
+    border-radius: @border-radius-base;
+    box-shadow: 0 1px 0 rgba(0, 0, 0, 0.2), 0 0 0 2px #fff inset;
+    color: #333;
+    display: inline-block;
+    font-size: .8em;
+    margin: 0 .1em;
+    padding: .1em .6em;
+    text-shadow: 0 1px 0 #fff;
+}