Add the technical explanation for the pop-up behavior

Author: MovByte

public/index.html

@@ -100,6 +100,7 @@
       try {
         const paymentResponse = await request.show();
       } catch (err) {
+        // See https://source.chromium.org/chromium/chromium/src/+/main:components/payments/core/native_error_strings.cc
         if (err instanceof DOMException && err.name === "AbortError") {
           switch (err.message) {
             case "Another PaymentRequest UI is already showing in a different tab or window.":
@@ -210,10 +211,9 @@
       pop-up. Try this multiple times.
     </p>
     <p>
-      <b>Explanation:</b> whenever it shows processing on the popup and you
-      reload at the same time it for some reason detaches into a pop-up. I don't
-      have the specific details of why this happens, but I will come back with
-      them soon.
+      <b>Technical explanation:</b> when the URL is supposed to render to a web
+      dialog modal view, but instead it falls back to a pop-up when it the web
+      dialog modal view is destroyed, because it is detached
     </p>
   </details>
   <details>