Add a warning about the future of the Google docs workaround (#2108)

ext/settings.html

@@ -1947,7 +1947,7 @@ <h1>Yomichan Settings</h1>
                 <div class="settings-item-left">
                     <div class="settings-item-label">
                         Force HTML-based rendering for Google Docs
-                        <a tabindex="0" class="more-toggle more-only" data-parent-distance="4">(?)</a>
+                        <a tabindex="0" class="more-toggle more-only danger-text" data-parent-distance="4">(?)</a>
                     </div>
                 </div>
                 <div class="settings-item-right">
@@ -1962,6 +1962,9 @@ <h1>Yomichan Settings</h1>
                     which prevents Yomichan from being able to scan text.
                     Enabling this option will force HTML-based rendering to be used.
                 </p>
+                <p class="danger-text">
+                    This is a workaround and it is likely that Google will unfortunately remove support for this workaround in the future.
+                </p>
                 <p>
                     <a tabindex="0" class="more-toggle" data-parent-distance="3">Less&hellip;</a>
                 </p>