Enable releasing packages from feature branches

[pomek]

Provide a description of the task

So far, the release scripts can be executed while the git repository is checked out to the #release branch.

However, we would like to enable releasing the code from feature branches, e.g., when preparing an alpha release, it could be performed from a feature branch containing an experimental feature.

Scope

• Allow generating the changelog and preparing packages to release from a custom branch.
  • The branch name could be specified via CLI, e.g., --branch alpha.
• Allow defining the latest release tag when generating the changelog. It can be useful when performing two alpha releases from different branches. By default, the tool uses a tag based on a version field in a package.json file.
  • When preparing an x.y.z-alpha.1 release, we should note that it is an update from x.y.z-alpha.0 instead of x.y.z.
  • The generator accepts the from option.

[pomek]

All required PRs are mentioned above. (☝️)