feat: upgrade bannertime via installation

[joemidi]

 Its Duncan
  _____                     _   _
 | __  |___ ___ ___ ___ ___| |_|_|_____ ___
 | __ -| . |   |   | -_|  _|  _| |     | -_|
 |_____|__,|_|_|_|_|___|_| |_| |_|_|_|_|___|

┌────────────────────────────────────────────────────┐
│ Update available: 2.2.9 current: 2.2.8             │
│ Run npm install -g generator-bannertime to update. │
└────────────────────────────────────────────────────┘

I've currently installed Bannertime via yarn global I would hope the prompt could remember that and give me the yarn version of updating.

[pyramidium]

Just updated the prompt to Run yarn global add generator-bannertime for consistency.