feat: Add monorepo support

[leo91000]

This is my attempt at adding monorepo support for changelogen.

It adds a recursive config option that will generate a changelog for every dir that have a package.json file.
You can optionnally specify a glob pattern to package.json (e.g : packages/**/package.json)

No matter if you specify a glob pattern or not, it will always includes root package.json file. This ensure we have a version for git tag

It basically rerun changelogen logic for every packages matched.
git log command will only get changes from the package directory

However I am not sure it supports every use cases

Maybe I should implement multiple strategies ?

[pi0]

Thank you for working on this dear @leo91000. I am moving mono repo support to #85 as tracker since it takes some steps to implement.