Add Thunderbird sponsorship banner to home, uploads and download page

app/ui/intro.js

@@ -1,5 +1,6 @@
 const html = require('choo/html');
 const raw = require('choo/html/raw');
+const assets = require('../../common/assets');
 
 module.exports = function intro(state) {
   const notice = state.WEB_UI.MAIN_NOTICE_HTML
@@ -12,6 +13,30 @@ module.exports = function intro(state) {
       `
     : '';
 
+  const sponsor = state.WEB_UI.SHOW_THUNDERBIRD_SPONSOR
+    ? html`
+        <a
+          class="w-full mt-5 mb-2 p-2 border-default dark:border-grey-70 rounded-default text-orange-60 bg-yellow-40 text-center leading-normal"
+          href="https://www.thunderbird.net/"
+        >
+          <svg
+            width="30"
+            height="30"
+            class="m-2 mr-3"
+            style="display: inline-block; vertical-align: middle;"
+          >
+            <image
+              xlink:href="${assets.get('thunderbird-icon.svg')}"
+              src="${assets.get('thunderbird-icon.svg')}"
+              width="30"
+              height="30"
+            />
+          </svg>
+          Sponsored by Thunderbird
+        </a>
+      `
+    : '';
+
   return html`
     <send-intro
       class="flex flex-col items-center justify-center bg-white px-6 md:py-0 py-6 mb-0 h-full w-full dark:bg-grey-90"
@@ -25,6 +50,7 @@ module.exports = function intro(state) {
           ${state.translate('introDescription')}
         </p>
       </div>
+      ${sponsor}
     </send-intro>
   `;
 };