Add the possibility to only generate the changelog and publish it on Github without bumping the version

[LouisMazel]

Describe the feature

Because the mono repository is not supported, I bump all my package versions independently and then I want to generate my changelog and publish it to Github with changelogen to take advantage of its simplicity and its beautiful format.

Today it's not possible to do it without bumping the version. It's only possible to "display only".

As I describe here, I found the solution but it's a little bit tricky:
#85 (comment)

Maybe you can open this option. I think you just need to edit this line, just bump when the --bump argument is present or add a new option to just handle generating, publishing, updating and such of the changelog.
https://github.com/unjs/changelogen/blob/176cb67ba4267d7a5cc64ad60aa823a02584c535/src/commands/default.ts#L69C3-L69C35

I can do a PR, let me know.

Additional information

• Would you be willing to help implement this feature?