A11Y: Add more information to the "reply to" button label. (#18604)

Includes the post number and poster's username for screen readers.

app/assets/javascripts/discourse/app/widgets/post-menu.js

@@ -239,6 +239,10 @@ registerButton("reply-small", (attrs) => {
     title: "post.controls.reply",
     icon: "reply",
     className: "reply",
+    translatedAriaLabel: I18n.t("post.sr_reply_to", {
+      post_number: attrs.post_number,
+      username: attrs.username,
+    }),
   };
 
   return args;
@@ -323,6 +327,10 @@ registerButton("reply", (attrs, state, siteSettings, postMenuSettings) => {
     title: "post.controls.reply",
     icon: "reply",
     className: "reply create fade-out",
+    translatedAriaLabel: I18n.t("post.sr_reply_to", {
+      post_number: attrs.post_number,
+      username: attrs.username,
+    }),
   };
 
   if (!attrs.canCreatePost) {

config/locales/client.en.yml

@@ -3210,6 +3210,7 @@ en:
       gap:
         one: "view %{count} hidden reply"
         other: "view %{count} hidden replies"
+      sr_reply_to: "Reply to post #%{post_number} by @%{username}"
 
       notice:
         new_user: "This is the first time %{user} has posted — let’s welcome them to our community!"