Add (fake) support for configs and secrets

[ulyssessouza]

What I did
Implemented fake configs and secrets through volume bindings

Both service inline and configs&secrets blocks work. For an example:

version: "3.7"
services:
  test:
    image: nginx
    configs:
      - my_config
      - source: ./my_inline.txt
        target: /root/my_inline_inside.txt
    secrets:
      - my_secret
      - source: ./my_inline_secret.txt
        target: /root/my_inline_secret_inside.txt

configs:
  my_config:
    file: ./my_config.txt

secrets:
  my_secret:
    file: ./my_secret.txt

Related issue
Resolves: #10
Resolves: #11

(not mandatory) A picture of a cute animal, if possible in relation with what you did