📖 Iroha 1 “Quick Start Guide” guide: updates to be added

[6r1d]

Iroha 1 part

The “Quick Start Guide” for Iroha 1 needs an update. It points out to a master branch that doesn't exist: git clone -b main https://github.com/hyperledger/iroha --depth=1. Is it correct to assume master was moved to main, as it is usually done, or are there other branches related to Iroha 1 Docker release?

Iroha 2 part

Since iroha2-dev may be moved to main, I'd prefer to update the doc knowing where the old main may go.

There are also differences between Asciinema demo on the page and the commands in the guide below it. Asciinema points to hyperledger/iroha-docker:master, while the command points to hyperledger/iroha:latest container.

I intend to upload a corrected version later.

[ThamaluM]

Please update it. I wasted some time forgetting GitHub changed the branch name convention.