Improve keyboard shortcuts descriptions (#8066)

* Add hotkey variants to keyboard shortcuts description

* Add documentation for “p” hotkey

* yarn manage:translations

app/javascript/mastodon/locales/defaultMessages.json

@@ -1254,6 +1254,10 @@
         "defaultMessage": "to mention author",
         "id": "keyboard_shortcuts.mention"
       },
+      {
+        "defaultMessage": "to open author's profile",
+        "id": "keyboard_shortcuts.profile"
+      },
       {
         "defaultMessage": "to favourite",
         "id": "keyboard_shortcuts.favourite"