Add basic styles for inline code (Fixes: #1142)

Author: milmazz

_epub/assets/less/app.less

@@ -1 +1,14 @@
+// Inline code
+code.inline {
+  font-family: courier, monospace;;
+  font-style: normal;
+  line-height: 24px;
+  font-weight: 400;
+  background-color: #f7f9fc;
+  vertical-align: baseline;
+  border-radius: 2px;
+  padding: .1em .2em;
+}
+
+// Highlight theme
 @import './code';