Repo config file for lint / format

Putting down some ideas for a potential new config file to be used by the new Nextflow lint and format commands.

Starting position:

• Can't use nextflow.config as separation of concerns, also potentially a bit recursive
• Want to make as generic as possible so it can be future-proofed (eg. not .nextflowignore to ignore files only, adaptable for more functionality)
• Common file format for easy interoperability

To make it clear what this is for, I'd suggest calling this thing nextflowrc, following the *nix convention with rc files for startup config / actions. It could be a hidden .nextflowrc.* dotfile or not, I could go either way.

With this, my initial stab is either YAML or TOML. Here's a very rough first draft with some suggestions for things that we may want to configure

nextflowrc.yml

lint:
   exclude:
      - "testing/*"
      - "docs/**/*.nf"
   output-format: concise
format:
   exclude:
      - modules
   spaces: 4
   harshil-alignment: true

Or toml, as used by pyproject.toml and netlify.toml etc:

nextflowrc.toml

[lint]
exclude = ["myworkdir/*", "snippets/**/*.nf"]
output-format = "extended"

[format]
exclude = ["modules"]
tabs = true
harshil-alignment = false

Note that we could support multiple formats, though I'm not sure that this would add much.

To avoid the proliferation of root-level config files, it may be possible for @nf-core to consider adopting this new file to replace .nf-core.yml (probably optionally), in an nf-core section in the file.

Thoughts + feedback welcome!

Start by reviewing the proposed Nextflow lint and format commands alongside nextflow.config and the suggested nextflowrc.yml or nextflowrc.toml formats. Consider how the proposed configuration could relate to .nf-core.yml, then establish a decided file name, format, and supported settings as the definition of done.