Updating readmes (#7950)
README for all templates still points to polkadot.network. update them to: 1. point to [docs.polkadot.com](http://docs.polkadot.com/) 2. point to official polkadot discord and @substratedevs in TG for support
README for all templates still points to polkadot.network. update them to: 1. point to [docs.polkadot.com](http://docs.polkadot.com/) 2. point to official polkadot discord and @substratedevs in TG for support