add announcement bar for the 2024 User Survey (#270)

Add an announcement bar to announce the 2024 Pantsbuild User Survey. I added some custom styles to (1) make the text larger and (2) to restore default link colors.

Screenshot: 
<img width="1788" alt="Screenshot 2024-10-08 at 22 59 11"
src="https://github.com/user-attachments/assets/d3b38cf4-e827-460d-bbd7-5c5b766ccc5d">

docusaurus.config.js

@@ -235,6 +235,11 @@ const config = {
   ],
 
   themeConfig: {
+    // Temporary: Announce the 2024 User Survey.
+    announcementBar: {
+      content:
+        'The Pantsbuild 2024 User Survey is live! Check out the <a href="/blog/2024/10/08/user-survey-2024">blog post</a> or <a target="_blank" href="https://forms.gle/eo7Y4DuxurjaMSZn6">take the survey</a>.',
+    },
     image: "img/social-card.png",
     navbar: {
       title: "Pantsbuild",

src/css/custom.css

@@ -36,3 +36,20 @@ figcaption {
 .color--success {
   color: var(--ifm-color-primary);
 }
+
+/* Announcement Bar styling */
+div[class*="AnnouncementBar"] {
+  /* Make the announcement text more prominent. */
+  font-size: 24px !important;
+}
+
+div[class*="AnnouncementBar"] a {
+  /* Default link style does not use a different color. */
+  color: var(--ifm-link-color);
+  text-decoration: inherit;
+}
+
+div[class*="AnnouncementBar"] a:hover {
+  color: var(--ifm-link-color);
+  text-decoration: underline;
+}