Add redirect from /tutorial (#7129)

Co-authored-by: Eric Windmill <eric@ericwindmill.com>

Author: parlough

firebase.json

@@ -458,6 +458,7 @@
       { "source": "/tools/sdk/archive", "destination": "/get-dart/archive", "type": 301 },
       { "source": "/tools/webstorm", "destination": "/tools#editors", "type": 301 },
       { "source": "/tos", "destination": "/terms", "type": 301 },
+      { "source": "/tutorial", "destination": "/learn/tutorial", "type": 301 },
       { "source": "/tutorials/dart-vm", "destination": "/tutorials/server", "type": 301 },
       { "source": "/tutorials/dart-vm/:page*", "destination": "/tutorials/server/:page*", "type": 301 },
       { "source": "/tutorials/language", "destination": "/language", "type": 301 },