CLOUDP-225858: add changelog command skeleton

[andreaangiolillo]

Proposed changes

Jira ticket: CLOUDP-225858

This PR creates the skeleton of the changelog command

 ./bin/foascli changelog create --help                                     
Generate the changelog for the OpenAPI spec.

Usage:
  foascli changelog create -b path_folder -r path_folder --dry-run ... [flags]

Aliases:
  create, generate

Flags:
  -b, --base string       Base folder where the command will store the output.
  -d, --dry-run           Dry run mode. The command will not write any files.
  -h, --help              help for create
  -r, --revision string   Folder where the command will store the output.