Add Rococo's contract chain as a chain option

[flipchan]

I'm requesting that Rococo's contract parachain to be added as a --chain option.

Is your feature request related to a problem? Please describe.
This is a request to add Rococo's contract chain to the --chain options. In order to make it easier to debug

Describe the solution you'd like
Rococo's contract chain to be added into crates/cargo-contract/src/cmd/prod_chains.rs:
https://github.com/use-ink/cargo-contract/blob/master/crates/cargo-contract/src/cmd/prod_chains.rs

Describe alternatives you've considered
I'm more than happy to submit a pr with the patch of this, if the maintainers think this is a good option.

Additional context
This would make it alot easier to debug Rococo contract chain's test contracts. The alternative right now is to manually define it as:
--url wss://rococo-contracts-rpc.polkadot.io