fix: Make the tooltip visible in IE10+ (#2452)

Notice:

This 'rect' is invisible as a container for the language symbol
to show the tooltip in both IE and Chrome, FF,ect.

For reasons of accessibility, user agents should always make the content
of the 'title' child element to the root svg element available to users.
However, this is typically done through other means than the tooltips
used for nested SVG and graphics elements, e.g., by displaying in a browser
tab.

See more at: https://svgwg.org/svg2-draft/struct.html#TitleElement

Issues and Subjects related to this are：
1、#2294.
2、#2403.
3、#2392.

Author: SEWeiTung

Diff for: layouts/partials/header.hbs

@@ -23,10 +23,11 @@
       </ul>
     </nav>
 
-    <svg id="lang-picker-toggler" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
-      <path d="M217.982 201.586h-64.499c-5.537 0-10.026 4.489-10.026 10.026s4.489 10.026 10.026 10.026h53.547c-4.72 25.263-26.935 44.446-53.547 44.446-30.037 0-54.473-24.436-54.473-54.473s24.436-54.473 54.473-54.473c14.55 0 28.229 5.667 38.518 15.955 3.916 3.916 10.264 3.916 14.178 0 3.916-3.916 3.916-10.264 0-14.178-14.077-14.077-32.791-21.829-52.697-21.829-41.094 0-74.525 33.431-74.525 74.525 0 41.094 33.431 74.525 74.525 74.525s74.525-33.431 74.525-74.525c.001-5.536-4.488-10.025-10.025-10.025z"/>
-      <path d="M470.331 92.24H269.728l-26.935-81.355a10.025 10.025 0 00-9.518-6.875H41.669C18.693 4.01 0 22.703 0 45.679v332.412c0 22.976 18.693 41.669 41.669 41.669h203.145l27.073 81.369a10.026 10.026 0 009.513 6.861h188.932c22.976 0 41.669-18.693 41.669-41.669V133.909c-.001-22.976-18.694-41.669-41.67-41.669zM41.669 399.708c-11.919 0-21.616-9.697-21.616-21.616V45.679c0-11.919 9.697-21.616 21.616-21.616h184.364l70.691 213.516a.366.366 0 00.015.043l53.664 162.086H41.669zm295.78-116.433c.805 1.11 10.824 14.877 26.355 34.066-4.377 5.756-9.015 11.474-13.91 17.036l-29.712-89.74h87.441c-6.196 13.031-16.938 33.813-31.692 55.736-13.553-16.921-22.069-28.622-22.249-28.87-3.251-4.482-9.519-5.481-14.002-2.23-4.482 3.25-5.48 9.518-2.231 14.002zM265.946 419.76h75.162l-55.503 59.084-19.659-59.084zm226.002 46.561c0 11.919-9.697 21.616-21.616 21.616H304.575l67.015-71.339-.004-.003c.293-.312.571-.64.823-.991a10.025 10.025 0 001.39-9.022l-16.688-50.402c7.073-7.406 13.68-15.143 19.805-22.965 13.299 15.772 29.037 33.446 45.778 50.187 1.957 1.957 4.524 2.937 7.089 2.937s5.132-.979 7.089-2.937c3.916-3.916 3.916-10.264 0-14.178-17.461-17.461-34.013-36.244-47.687-52.632 21.251-30.503 35.033-59.504 40.535-71.954h21.454c5.537 0 10.026-4.489 10.026-10.026s-4.489-10.026-10.026-10.026h-66.173v-18.047c0-5.537-4.489-10.026-10.026-10.026s-10.026 4.489-10.026 10.026v18.046h-51.406l-37.178-112.292H470.33c11.919 0 21.616 9.697 21.616 21.616v332.412z"/>
-    </svg>
+  <svg id="lang-picker-toggler" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
+    <rect id="lang-rect" width="512" height="512" x="0" y="0" fill="none" pointer-events="fill"/>
+    <path d="M217.982 201.586h-64.499c-5.537 0-10.026 4.489-10.026 10.026s4.489 10.026 10.026 10.026h53.547c-4.72 25.263-26.935 44.446-53.547 44.446-30.037 0-54.473-24.436-54.473-54.473s24.436-54.473 54.473-54.473c14.55 0 28.229 5.667 38.518 15.955 3.916 3.916 10.264 3.916 14.178 0 3.916-3.916 3.916-10.264 0-14.178-14.077-14.077-32.791-21.829-52.697-21.829-41.094 0-74.525 33.431-74.525 74.525 0 41.094 33.431 74.525 74.525 74.525s74.525-33.431 74.525-74.525c.001-5.536-4.488-10.025-10.025-10.025z"/>
+    <path d="M470.331 92.24H269.728l-26.935-81.355a10.025 10.025 0 00-9.518-6.875H41.669C18.693 4.01 0 22.703 0 45.679v332.412c0 22.976 18.693 41.669 41.669 41.669h203.145l27.073 81.369a10.026 10.026 0 009.513 6.861h188.932c22.976 0 41.669-18.693 41.669-41.669V133.909c-.001-22.976-18.694-41.669-41.67-41.669zM41.669 399.708c-11.919 0-21.616-9.697-21.616-21.616V45.679c0-11.919 9.697-21.616 21.616-21.616h184.364l70.691 213.516a.366.366 0 00.015.043l53.664 162.086H41.669zm295.78-116.433c.805 1.11 10.824 14.877 26.355 34.066-4.377 5.756-9.015 11.474-13.91 17.036l-29.712-89.74h87.441c-6.196 13.031-16.938 33.813-31.692 55.736-13.553-16.921-22.069-28.622-22.249-28.87-3.251-4.482-9.519-5.481-14.002-2.23-4.482 3.25-5.48 9.518-2.231 14.002zM265.946 419.76h75.162l-55.503 59.084-19.659-59.084zm226.002 46.561c0 11.919-9.697 21.616-21.616 21.616H304.575l67.015-71.339-.004-.003c.293-.312.571-.64.823-.991a10.025 10.025 0 001.39-9.022l-16.688-50.402c7.073-7.406 13.68-15.143 19.805-22.965 13.299 15.772 29.037 33.446 45.778 50.187 1.957 1.957 4.524 2.937 7.089 2.937s5.132-.979 7.089-2.937c3.916-3.916 3.916-10.264 0-14.178-17.461-17.461-34.013-36.244-47.687-52.632 21.251-30.503 35.033-59.504 40.535-71.954h21.454c5.537 0 10.026-4.489 10.026-10.026s-4.489-10.026-10.026-10.026h-66.173v-18.047c0-5.537-4.489-10.026-10.026-10.026s-10.026 4.489-10.026 10.026v18.046h-51.406l-37.178-112.292H470.33c11.919 0 21.616 9.697 21.616 21.616v332.412z"/>
+  </svg>
 
     <div class="lang-picker hidden">
       <ul id="language-items">
@@ -64,11 +65,13 @@
     }
   })
 
+  // Find the container where to mark the tooltip
+  var langRect = document.querySelector('#lang-picker-toggler > #lang-rect');
   // Create dynamically label for tooltip
   var titleEle = document.createElementNS('http://www.w3.org/2000/svg', 'title');
   var textString = document.createTextNode(currentLangElement.getAttribute('data-language'));
   titleEle.appendChild(textString);
-  langPickerTogglerElement.appendChild(titleEle);
+  langRect.appendChild(titleEle);
 
   // Remove the current selected language item, because we don't need to choose it
   // any more unless we want to switch the new language