Release-type input overrides config file

### 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_