Add documentation for updating to stable

[adbsmith]

Congrats on the release of v1.0.0! I was thinking that it might be useful to have some documentation on updating from the beta releases to the new stable release so that folks are aware of any migration steps (if any) they should take.

[hayu-hayu]

I updated from 0.0.6 (HA add-on) without doing any migration steps - no issues so far.