Release-type input overrides config file

[kerruba-milkman]

TL;DR

Having both config-file and release-type as inputs will make the release-type input override (or add) the release-type to all packages in the config file

Detailed design

Currently when passing both the release-type and config-file inputs, the config-file input is actually ignored and a default configuration file is generated using the release-type input.
A scenario that I'm working on right know is to centralize the configuration file for different repositories - I always need to update certain 'extra-files' - and override the release-type using a Variable in the repository. I thought this was possible, but found out reading the code is not the how the action is meant to be used.

If having the release-type + config-file merging strategy not possible for any reason, at least documenting it in the README would be useful to avoid confusion

Additional information

No response