spell out that EW does *not* work on mobile. (#29211)

* spell out that EW does *not* work on mobile.

see https://bsky.app/profile/jeroenheijmans.nl/post/3lhiwcrtdt22x

* lint

---------

Co-authored-by: David Langley <[email protected]>
Co-authored-by: David Langley <[email protected]>

Author: ara4n

src/vector/mobile_guide/index.html

@@ -782,6 +782,8 @@ <h2>2: Configure your app</h2>
             <div class="mx_HomePage_row mx_Center mx_Spacer">
                 <p class="mx_Spacer">
                     <a id="back_to_element_button" href="#" class="mx_FooterLink"> Go to Desktop Site </a>
+                    <br />
+                    Please note the Desktop site does <b>not</b> work on mobile.
                 </p>
             </div>
         </div>