Support multiple template repos

[tschm]

I want something along the lines of

templates:
  - repository: jebel-quant/rhiza
    branch: main
    include:
      - .github
      - Makefile
    exclude:
      - .github/secrets.yml

  - repository: jebel-quant/rhiza-extensions
    branch: dev
    include:
      - extra-config
      - scripts

This handles multiple repos sequentially. Later repos can overwrite files from earlier repos, giving you a natural priority system.

[tschm]

Very useful for latex

[tschm]

There are some misleading comments in the CLI.md file