Replace old resizing code with CSS flex

src/css/dashboard.css

@@ -1,14 +1,18 @@
 html, body {
-    height: 100%;
+    display: flex;
+    flex-direction: column;
+    height: 100vh;
+    justify-content: stretch;
     overflow: hidden;
     position: relative;
-    width: 100%;
+    width: 100vw;
     }
 #dashboard-nav {
     background-color: var(--default-surface);
     border: 0;
     box-shadow: var(--dashboard-bar-shadow);
     display: flex;
+    flex-shrink: 0;
     flex-wrap: wrap;
     overflow-x: hidden;
     padding: 0;
@@ -48,6 +52,7 @@ html, body {
 iframe {
     background-color: transparent;
     border: 0;
+    flex-grow: 1;
     margin: 0;
     padding: 0;
     width: 100%;

src/js/dashboard.js

@@ -30,16 +30,6 @@
 
 /******************************************************************************/
 
-const resizeFrame = function() {
-    const navRect = document.getElementById('dashboard-nav')
-                            .getBoundingClientRect();
-    const viewRect = document.documentElement.getBoundingClientRect();
-    document.getElementById('iframe').style.setProperty(
-        'height',
-        (viewRect.height - navRect.height) + 'px'
-    );
-};
-
 const discardUnsavedData = function(synchronous = false) {
     const paneFrame = document.getElementById('iframe');
     const paneWindow = paneFrame.contentWindow;
@@ -121,12 +111,9 @@ vAPI.messaging.send('dashboard', {
     document.body.classList.toggle('canUpdateShortcuts', response === true);
 });
 
-resizeFrame();
-
 vAPI.localStorage.getItemAsync('dashboardLastVisitedPane').then(value => {
     loadDashboardPanel(value !== null ? value : 'settings.html', true);
 
-    window.addEventListener('resize', resizeFrame);
     uDom('.tabButton').on('click', onTabClickHandler);
 
     // https://developer.mozilla.org/en-US/docs/Web/API/Window/beforeunload_event