Add stylelint config icon tooltip

_locales/en/messages.json

@@ -354,6 +354,10 @@
       }
     }
   },
+  "stylelintConfig": {
+    "message": "Open a popup to configure stylelint rules",
+    "description": "Tooltip on an icon to indicate it opens a popup with stylelint configuration settings"
+  },
   "manageFilters": {
     "message": "Filters",
     "description": "Label for filters container"

edit.html

@@ -198,9 +198,11 @@
             <option value="csslint" selected>CSSLint</option>
             <option value="stylelint">stylelint</option>
           </select>
+          <span class="linter-settings" i18n-title="stylelintConfig">
             <svg id="stylelint-settings" class="svg-icon settings">
               <use xlink:href="#svg-icon-settings"/>
             </svg>
+          </span>
       </section>
       <section id="lint"><h2 i18n-text="issues">: <span id="issue-count"></span><svg id="lint-help" class="svg-icon info"><use xlink:href="#svg-icon-help"/></svg></h2><div></div></section>
     </div>

edit/edit.css

@@ -387,7 +387,8 @@ body[data-match-highlight="selection"] .CodeMirror-selection-highlight-scrollbar
 #help-popup .error a {
   color: #f00;
 }
-#help-popup .error.show {
+#help-popup .error.show,
+#options .linter-settings {
   display: inline-block;
 }