enhance(blueprint): Accept input from stdin

[LaurenceJJones]

Community Contribution License Agreement

By creating this pull request, I grant the project maintainers an unlimited,
perpetual license to use, modify, and redistribute these contributions under any terms they
choose, including both the AGPLv3 and the Fossorial Commercial license terms. I
represent that I have the right to grant this license for all contributed content.

Description

Allow users to pipe output of commands to stdin for the blueprint file, this is useful when you want to send a blueprint file but dont want to leave any artifacts on disk.

How to test?

echo "public-resources:
  marmot-http:
    name: Marmot HTTP
    protocol: http
    full-domain: test.example.com
    targets:
      - site: classic-yellow-bellied-marmot
        hostname: localhost
        method: http
        port: 80" | pangolin apply blueprint --file -