setbgm - new addon

I figured out how the Orchestrion sets the background music in your Mog House and this lets you set it to any music in the game.
`windower.ffxi.get_*` calls are usually pretty expensive. You can cache the result and re-use it later in the function so you don't have to call it twice:
```lua
    local info = windower.ffxi.get_int()
    if not info.mog_house or info.zone == 280 then
```