Add support for joi-browser.

[Veetaha]

I am sorry, if there indeed exists a clever way to use joi-browser when importing this library, but I failed to find it. May ask you to add a file like typesafe-joi/browser that would export joi-browser instead of plain joi and use the same typings?

[hjkcai]

Yes, but joi-browser is out of date. It may not match the behavior of the current joi. @jeffbski

I prefer creating a new package because the official joi does not have browser version at all. So typesafe-joi should not have neither.

[hjkcai]

@jeffbski Could you please test if joi-browser is compatible with the latest joi? I would like to submit a PR to integrate typesafe-joi into joi-browser.