Improve accessibility (#4369)

* fix(compose): Use nav and remove redundant aria-label

* fix(tabs_tab): Use nav and add aria-label

* fix(app): Add aria-label for settings toggle button

* chore: Run yarn manage:translations

app/javascript/mastodon/locales/defaultMessages.json

@@ -53,6 +53,14 @@
   },
   {
     "descriptors": [
+      {
+        "defaultMessage": "Show settings",
+        "id": "column_header.show_settings"
+      },
+      {
+        "defaultMessage": "Hide settings",
+        "id": "column_header.hide_settings"
+      },
       {
         "defaultMessage": "Unpin",
         "id": "column_header.unpin"
@@ -138,6 +146,10 @@
         "defaultMessage": "Reply",
         "id": "status.reply"
       },
+      {
+        "defaultMessage": "Share",
+        "id": "status.share"
+      },
       {
         "defaultMessage": "Reply to thread",
         "id": "status.replyAll"