Adds instructions to generate the icon font in the README

icon_font/template.jst.ejs

@@ -18,7 +18,6 @@
   -moz-osx-font-smoothing: grayscale;
   line-height: 1;
 }
-
 <% _.each(glyphs, function(glyph) { %>
 <%= '/* SG' %>
 <%= '# Icon font/' + glyph.fileName.split("_")[2]  %>
@@ -26,6 +25,7 @@
 <i class="iconFont iconFont-<%= glyph.fileName.split("_")[2] %> iconFont--size24"></i>
 ```
 <%= '*/' %>
+
 .iconFont-<%= glyph.fileName.split("_")[2] %>::before {
   content: '\<%= glyph.codePoint %>';
 }