Bring back the Gen2 docs

I went to https://docs.convox.com today and noticed that the link to the Gen2 docs are missing. As we still maintain Gen2 applications, those docs are pertinent to us. Given that Convox doesn’t indicate that Gen2 is unsupported, I would expect that the Gen2 docs would remain available.

Found this by playing around with the domain :man_shrugging: Convox Docs