Improve the documentation with versioning explanation

[alebaffa]

Hello,

I was looking for a definitive explanation about the versioning used in Substrate, more specifically what are the differences between the master branch, monthly release tag, polkadot-v.x.x.x branches, etc., but I did not find anything official.
I received some good answers in the Polkadot Discord (here)

Monthly "releases" are not reliable nearly in the same manner as the Polkadot companion releases of substrate. I would highly suggest using those instead. We don't have a substrate specific release cycle at this time. Only a Polkadot one.
The Polkadot branches/tags are ones that the core team robustly test and when incorporated in Polkadot itself. some releases don't get into a runtime, some only kusama for example, so master branch effectively becomes a staging of features to eventually be brought in via governance to kusmama, the when audits pass and the network is reqdy to polkadot. For things to land in the runtime for Polkadot, audits are explicitly required.
Some features are only exposed to rococo or versi for testing purely in a testnet that live in the Polkadot code base.
All that to say, it is not very easy to gather where things are at in the pipeline nor what versions you likely want outside latest Polkadot release branch.
For most, the latest release is what you need to depend on to be a parachain FYI.

and I also found this question/answer in Substrate Stack Exchange.

I think this would be a very important point to clearly describe in the official documentation. This choice can turn out to be a critical decision since it could make a project very complicated to maintain. Which branch to choose?.
It is a missing piece of knowledge that would help to improve the development experience with Substrate in general, I think.