Adding default settings for new repositories creation

There is `git-repo config` that I am trying not to confuse. This issue is about configuring GitHub, GitLab, Bitbucket and not configuring git-repo. Maybe this is out of scope and fits in better with something such as Terraform.io

Problem:
Repos will have a handful of settings, such as enabled services, branch protection, webhooks, merge types, mirroring, etc. Click though web gui introduces inconsistencies and other disadvantages.

If my org were to primarily use GitLab but mirror on GitHub then there are two namespaces to clear and two different configurations to deal with.

Proposed:
Configuration of provider repos in yaml, json (with comments, just minify to strip first), or toml.
A cmd to act on the configuration file such as `hub|lab|bit|all create|update|remove`

`git all create` would create whatever repos are configured, in my case, github and gitlab.

Start by reviewing the existing `git-repo config` command and the repository's CLI entry points, then compare how GitHub, GitLab, and Bitbucket settings would map to the proposed YAML, JSON, or TOML configuration. The provider scope and command behavior need to be settled first; done would mean a documented configuration format and working create, update, and remove flows across the selected providers.

Written by the indexing model from the issue text.