Implement new design for Welcome page (#33211)

* Convert welcome.html to React component

In advance of changes to use Compound

* Fix types

* Fix tests

* Update styling to match Figma

* Fix random capitalisation

* Tweak styling

* Regenerate i18n

* Update tests

* Make linter happy

* Iterate

apps/web/res/css/views/auth/_Welcome.pcss

@@ -9,6 +9,10 @@ Please see LICENSE files in the repository root for full details.
     display: flex;
     flex-direction: column;
     align-items: center;
+    background-color: var(--cpd-color-bg-canvas-default);
+    box-sizing: border-box;
+    padding: var(--cpd-space-11x) var(--cpd-space-12x) var(--cpd-space-4x);
+
     &.mx_WelcomePage_registrationDisabled {
         .mx_ButtonCreateAccount {
             display: none;
@@ -18,7 +22,7 @@ Please see LICENSE files in the repository root for full details.
 
 .mx_Welcome .mx_AuthBody_language {
     width: 160px;
-    margin-bottom: 10px;
+    margin: var(--cpd-space-1x) 0;
 }
 
 /* Invert image colours in dark mode. */