Add styling guide link to custom CSS section.

package.json

@@ -9,6 +9,7 @@
     "downloads": "https://www.4chan-x.net/builds/",
     "oldVersions": "https://raw.githubusercontent.com/ccd0/4chan-x/",
     "faq": "https://github.com/ccd0/4chan-x/wiki/Frequently-Asked-Questions",
+    "cssGuide": "https://github.com/ccd0/4chan-x/wiki/Styling-Guide",
     "license": "https://github.com/ccd0/4chan-x/blob/master/LICENSE",
     "changelog": "https://github.com/ccd0/4chan-x/blob/master/CHANGELOG.md",
     "issues": "https://gitreports.com/issue/ccd0/4chan-x",

src/General/Settings/Advanced.html

@@ -137,6 +137,7 @@
   <legend>
     <label><input type="checkbox" name="Custom CSS"> Custom CSS</label>
   </legend>
+  <div>For more information about customizing 4chan X&#039;s CSS, see the <a href="<%= meta.cssGuide %>" target="_blank">styling guide</a>.</div>
   <button id="apply-css">Apply CSS</button>
   <textarea name="usercss" class="field" spellcheck="false"></textarea>
 </fieldset>