UX: detect DiscourseHub user agent in recently used devices

config/locales/server.en.yml

@@ -746,6 +746,7 @@ en:
       opera: "Opera"
       ie: "Internet Explorer"
       edge: "Microsoft Edge"
+      discoursehub: "DiscourseHub app"
       unknown: "unknown browser"
     device:
       android: "Android Device"

lib/browser_detection.rb

@@ -14,6 +14,8 @@ module BrowserDetection
       :safari
     when /MSIE/i, /Trident/i
       :ie
+    when /DiscourseHub/i
+      :discoursehub
     else
       :unknown
     end