Update documentation website - seems very out of date

The protoc command on the example page on the website wasn't working for me: https://twitchtv.github.io/twirp/docs/example.html

I hacked at it for a bit and came up with an incantation that worked.

I came to update the docs page and noticed that the markdown version of the documentation seems to have the correct command.

It was fixed last year, here: https://github.com/twitchtv/twirp/commit/97820de62b5d26f7f7447e7480d1b83eb44d5356

I think the website just needs re-generated.