Add padding to make styling consistent

[MAILPOET-2745]

assets/css/src/components/formEditor/components/_header.scss

@@ -0,0 +1,9 @@
+.mailpoet-editor-header-button {
+  padding-left: 8px;
+  padding-right: 8px;
+
+  @media (min-width: 600px) {
+    padding: 0 12px;
+    margin-right: 12px;
+  }
+}

assets/css/src/formEditor.scss

@@ -8,6 +8,7 @@
 @import '../../../node_modules/codemirror/lib/codemirror';
 @import '../../../node_modules/codemirror/theme/neo';
 @import './components/formEditor/components/form_title';
+@import './components/formEditor/components/header';
 @import './components/formEditor/components/sidebar';
 @import './components/formEditor/components/preview';
 @import './components/formEditor/components/block_editor';

assets/js/src/form_editor/components/header.jsx

@@ -47,6 +47,7 @@ export default () => {
           tooltipPosition="down"
           onClick={() => toggleSidebar(!sidebarOpened)}
           isPressed={sidebarOpened}
+          className="mailpoet-editor-header-button"
         />
       </div>
       <div className="edit-post-header__toolbar">
@@ -55,6 +56,7 @@ export default () => {
             isSecondary
             isLarge
             href="?page=mailpoet-forms#/"
+            className="mailpoet-editor-header-button"
           >
             {MailPoet.I18n.t('back')}
           </Button>