Add support for a config file

[bayou-brogrammer]

I think supporting a config file like .bluebuild or something similar could be beneficial in the future.

As our cli commands grows, users might have to enter more and more flags to get bluebuild to act how they intend, but having a config file to read from could save them from typing or using the same command over and over.

[xynydev]

I don't like the ".bluebuild" because it's a dotfile with an unspecified directory. I'm also not sure how the different commands would work if the config file was for setting args.

Maybe a flat bluebuild.toml file in each project directory like below could work.

# bluebuild.toml
[build]
arg1 = "value"
push = true
[generate]
output = "out.Containerfile"

bluebuild build --config-file bluebuild.toml

Or, I'm not sure why I thought of toml first, since we already also use yaml.

build:
  arg1: value
  push: true
generate:
  output: out.Containerfile

bluebuild generate --config-file bluebuild.yml

Might also want different configs for the same thing, but not sure how that should be structured.

commands:
   - name: build-ghcr
     type: build
     push: true
     registry-path: ghcr.io
   - name: build-gitlab
     type: build
     push: true
     registry-path: registry.gitlab.io

bluebuild --commands-file bluebuild.yaml build-gitlab --recipe config/recipe-kde.yml