Increase the start countdown in JSON

[Atdit]

Describe the feature you'd like
On gamemodes where you can only join in the pre-match status, increase the default countdown until it starts from 20 to 30 seconds. This will result in less players forgetting to join and not being able to after the game starts.
Yes, on Infected you can join after the game starts, but you won't get the chance to be Human.

Usefulness of the feature
Less players will be left as spectators (or become an Infected)

Additional context
It would also be nice to have title show or a special message in text, which tells you that you're only able to join right now if you want to be Human (Infected) or if you want to play at all (Blitz).

[BennyDoesStuff]

I think the best way to handle this is to have an option in the JSON to determine the start countdown for that map, but I might be wrong here.