prepare release command

[JonasJurczok]

To generate all info needed for a release this command should do the following:

• collect changes from the changelog (last tag -> now)
• create changelog entry
• changelog entry should follow a simple syntax to distinguish bugfixes from features and breaking changes
• bump mod version accordingly

workflow:

• work on feature branches and merge to master
• locally create new branch
• run faketorio prepare-release
• commit, PR, merge
• build release

simple workflow:

• work on feature branch
• when work finished run prepare release
• include changelog and info.json changes in the PR