Added skip-menu link for keyboard users.

src/components/Toolbar.jsx

@@ -135,9 +135,13 @@ export default class Toolbar extends React.Component {
       />
       <div className="maputnik-toolbar__inner">
         <ToolbarLink
+          tabIndex="2"
           href={"https://github.com/maputnik/editor"}
           className="maputnik-toolbar-logo"
         >
+          <a tabIndex="1" className="maputnik-toolbar-skip" href="#skip-menu">
+            Skip the menu
+          </a>
           <img src={logoImage} alt="Maputnik" />
           <h1>Maputnik
             <span className="maputnik-toolbar-version">v{pkgJson.version}</span>

src/components/layers/LayerList.jsx

@@ -209,6 +209,7 @@ class LayerListContainer extends React.Component {
         <div className="maputnik-default-property">
           <div className="maputnik-multibutton">
             <button
+              id="skip-menu"
               onClick={this.toggleLayers.bind(this)}
               className="maputnik-button">
               {this.state.areAllGroupsExpanded === true ? "Collapse" : "Expand"}