docs: added github corner

Author: castle055

docs/assets/overrides.css

@@ -18,4 +18,20 @@ html {
 
 .arrow {
     font-size: 100%;
-}
+}
+
+.github-corner svg {
+    fill: var(--primary-light-color);
+    fill: #FCAE1E;
+    color: var(--page-background-color);
+    width: 72px;
+    height: 72px;
+}
+
+@media screen and (max-width: 768px) {
+    .github-corner svg {
+        width: 40px;
+        height: 40px;
+    }
+}
+

docs/header.html

@@ -50,6 +50,12 @@
 <div id="side-nav" class="ui-resizable side-nav-resizable"><!-- do not remove this div, it is closed by doxygen! -->
     <!--END FULL_SIDEBAR-->
     <!--END DISABLE_INDEX-->
+    <a href="https://github.com/castle055/cpp-reflect" class="github-corner" title="View source on GitHub" target="_blank" rel="noopener noreferrer">
+        <svg viewBox="0 0 250 250" width="40" height="40" style="position: absolute; top: 0; border: 0; right: 0; z-index: 99;" aria-hidden="true">
+            <path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path>
+            <path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2" fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path><path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z" fill="currentColor" class="octo-body"></path>
+        </svg>
+    </a>
 
     <div id="top"><!-- do not remove this div, it is closed by doxygen! -->
 
@@ -86,7 +92,6 @@
                 <!--BEGIN SEARCHENGINE-->
                 <!--BEGIN FULL_SIDEBAR-->
                 <tr><td colspan="2">$searchbox</td></tr>
-                <tr><td colspan="2">$searchbox</td></tr>
                 <!--END FULL_SIDEBAR-->
                 <!--END SEARCHENGINE-->
                 </tbody>