Add @triggerHtmlTag in docs and add notes to migrate to v9.x (#1034)

Author: mkszepp

docs/app/templates/public-pages/docs/api-reference.gts

@@ -122,6 +122,11 @@ import { LinkTo } from '@ember/routing';
         <td>The component to render as trigger instead of the default trigger
           component.</td>
       </tr>
+      <tr>
+        <td>triggerHtmlTag</td>
+        <td><code>String</code></td>
+        <td>(Default: <code>'div'</code>) The tag of the trigger component</td>
+      </tr>
       <tr>
         <td>verticalPosition</td>
         <td><code>String</code></td>
@@ -209,7 +214,10 @@ import { LinkTo } from '@ember/routing';
       <tr>
         <td>htmlTag</td>
         <td>String</td>
-        <td>(Default: <code>'div'</code>) The tag of the trigger component</td>
+        <td>(Default:
+          <code>'div'</code>) The tag of the trigger component (Note: If you are
+          using the yielded trigger component, please use
+          <code>@triggerHtmlTag</code>)</td>
       </tr>
       <tr>
         <td>title</td>

docs/app/templates/public-pages/docs/migrate-8-0-to-9-0.gts

@@ -54,14 +54,14 @@ import { LinkTo } from '@ember/routing';
     </li>
     <li>
       <p>
-        Passing
-        <code>@dropdownId</code>
-        wasn't working correctly without using custom modifiers and was
-        undocumented. Remove this parameter and use the
-        <code>uniqueId</code>
-        property from the public API instead.
+        If you are using
+        <code>@htmlTag</code>
+        on the yielded trigger component (for example,
+        <code>&lt;dd.Trigger @htmlTag="span"&gt;</code>) replace it with
+        <code>&lt;BasicDropdown @triggerHtmlTag="span"&gt;</code>
+        This change is required to fix Glint v2 typing issues.
         <br />
-        <small><i>(Deprecation added in 8.8)</i></small>
+        <small><i>(Deprecation added in 8.10)</i></small>
       </p>
     </li>
     <li>
@@ -91,6 +91,18 @@ import { LinkTo } from '@ember/routing';
         <small><i>(Deprecation added in 8.9)</i></small>
       </p>
     </li>
+    <li>
+      <p>
+        Passing
+        <code>@dropdownId</code>
+        wasn't working correctly without using custom modifiers and was
+        undocumented. Remove this parameter and use the
+        <code>uniqueId</code>
+        property from the public API instead.
+        <br />
+        <small><i>(Deprecation added in 8.8)</i></small>
+      </p>
+    </li>
   </ul>
 
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