fix(ui): ensure draggable titlebar

Bring bak the titlebar so that the window can be moved, but make it
transparent and pinned to the top of the window.

app/components/App/App.scss

@@ -11,6 +11,9 @@
 }
 
 .titleBar {
+  height: 20px;
+  width: 100%;
+  position: absolute;
   -webkit-user-select: none;
   -webkit-app-region: drag;
 }

app/components/Onboarding/FormContainer/FormContainer.js

@@ -14,6 +14,7 @@ import styles from './FormContainer.scss'
 
 const FormContainer = ({ title, description, back, next, children, theme }) => (
   <div className={styles.container}>
+    <div className={styles.titleBar} />
     <header className={styles.header}>
       <section>
         <Isvg src={theme === 'light' ? zapLogoBlack : zapLogo} />

app/components/Onboarding/FormContainer/FormContainer.scss

@@ -6,6 +6,14 @@
   background: var(--darkestBackground);
 }
 
+.titleBar {
+  height: 20px;
+  width: 100%;
+  position: absolute;
+  -webkit-user-select: none;
+  -webkit-app-region: drag;
+}
+
 .header {
   display: flex;
   flex-direction: row;