Allow .editorconfig for prettier

[joedevivo]

What does this PR do?

prettier wasn't respecting my .editorconfig. This PR creates an option format.editorConfig, and when it's true, will pass that into prettier, respecting those settings if you opt in.

What issues does this PR fix or reference?

Is it tested? How?

Built locally, tested in neovim with nvim-lspconfig.

opts = {
  servers = {
    yamlls = {
      cmd = "path/to/local/yaml-language-server",
      settings = {
        yaml = {
          format = {
            enable = true,
            editorConfig = true,
          },
        },
      },
    },
  },
}

[coveralls]

coverage: 83.961%. remained the same
when pulling 6b1b261 on joedevivo:editorconfig
into d17039f on redhat-developer:main.

[datho7561]

In the current configuration, what does this setting default to? I think it would be helpful to enable it by default, unless you think that will be annoying (if someone has configured formatting settings in an .editorconfig they probably want them respected)

[datho7561]

I don't think this works (I've tested manually in VS Code and it doesn't seem to work). I don't see editorConfig as a parameter in the documentation. To get it to work, you'll need to fetch the config for the file using https://prettier.io/docs/api#prettierresolveconfigfileurlorpath--options, then use the result from that as the config in the call to format instead of the prettierOptions defined here. (or, somehow handle merging the fetched prettier/editorconfig with what the language server has been told).