Provide a way to conveniently give star Armeria from the site (#4476)

Motivation:

If a user stays on Armeria site (https://armeria.dev) for more than 10 seconds, we can assume they might be interested in our project and like to star Armeria on GitHub.

Modifications:

- Add a small banner to the left corner of the Armeria site.
  - It will be exposed 10 seconds after a user visits.

Result:

Gentle star marketing

site/package.json

@@ -86,6 +86,7 @@
     "react-dom": "^17.0.2",
     "react-easy-emoji": "^1.6.1",
     "react-helmet": "^6.1.0",
+    "react-iframe-click": "^2.0.2",
     "react-mixitup": "^2.3.0",
     "react-reveal": "^1.2.2",
     "react-sticky-box": "^1.0.2",

site/src/layouts/base.tsx

@@ -13,6 +13,7 @@ import Footer from './footer';
 import * as styles from './base.module.less';
 import flashAtHash from './flash-at-hash';
 import jumpToHash from './jump-to-hash';
+import StarBegging from './star-begging';
 
 const { Content } = Layout;
 
@@ -116,6 +117,7 @@ const BaseLayout: React.FC<BaseLayoutProps> = (props) => {
         )}
         <Footer />
       </Layout>
+      <StarBegging />
       <CookieConsent
         declineButtonText="Opt out"
         containerClasses={styles.cookieConsentContainer}

site/src/layouts/star-begging.module.less

@@ -0,0 +1,42 @@
+#starBegging {
+  transition: transform .25s;
+  transform: scale(0);
+  border-radius: 8px;
+  position: fixed;
+  bottom: 32px;
+  right: 32px;
+  padding: 20px 40px 16px 20px;
+  background: #fff;
+  box-shadow: 0 1px 20px rgba(0, 0, 0, 0.15);
+  z-index: 9999998;
+
+  p {
+    font-size: 16px;
+    margin: 0 0 15px;
+  }
+
+  .close {
+    position: absolute;
+    right: 20px;
+    top: 20px;
+    height: 40px;
+    width: 40px;
+    line-height: 1;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    font-size: 28px;
+    font-family: arial, sans-serif;
+    cursor: pointer;
+    background: rgba(0, 0, 0, 0.05);
+    border-radius: 5px;
+  }
+}
+
+#starBegging.on {
+  transform: scale(1);
+}
+#starBegging.off {
+  transform: translateX(400px);
+}
+