translatable: true works but translatable: 1 not

I noticed that `translatable: true` works but some naughty users like me might try `translatable: 1` (what I expected to work since the true/fase/1/0 can also be mixed in bolt's other yml files.

If it's easy to change that in the core: great! 
Otherwise a small addition to the docs might be a good ideaand you know what: I'll PR that right away.