Update generating manifests document

[mkuziemko]

Description

On the website, there is a document that described the generating manifests. Unfortunately, it is outdated. The goal of this task is to update it.

• replace capact alpha manifest-gen to capact manifest generaten
• make sure that all current descriptions and generated files are up to date,
• add a description of the interactive mode and new features.

Related PRs

• https://github.com/capactio/capact/pull/613
• https://github.com/capactio/capact/pull/596

[mkuziemko]

Manifests updated, although we should also describe an interactive mode.