Add ability to change the name

[g-ortuno]

Now that we know we can change the name using Characteristic 0xffff we should make use of it on the webpage!

[beaufortfrancois]

You can already do it from https://webbluetoothcg.github.io/demos/playbulb-candle/ ;) See https://github.com/WebBluetoothCG/demos/blob/gh-pages/playbulb-candle/app.js#L32