add option to tweak programmatically the configuration

[raulfdm]

Description

The user should be allowed to extend the configuration programmatically. This will be handy for automation/scripting.

import { updateConfig, defineRule } from "@codeowners-flow/cli/config";

await updateConfig((currentConfig) => {
  currentConfig.rules = defineRule({
    patterns: ["module/logger"],
    owners: ["@company/infra"],
  });

  return currentConfig;
});

Because the user gets the current config, it might be useful to provide a field like _meta so they can add and maintain info in the config level but also have access, like:

// codeowners.config.mjs

const mainTeam = { name: '@company/core-team' };

/** @type {import('@codeowners-flow/cli/config').UserConfig} */
export default {
  outDir: '.github',
  _meta: {
    mainTeam, // HERE
  },
  rules: [
    {
      patterns: ['*'],
      owners: [mainTeam],
    },
  ],
};

Then:

import { updateConfig, defineRule } from "@codeowners-flow/cli/config";

await updateConfig((currentConfig) => {
  currentConfig.rules = defineRule({
    patterns: ["module/logger"],
    owners: ["@company/infra", currentConfig._meta.mainTeam], // CONSUMING HERE
  });

  return currentConfig;
});

I'm not sure how to make this type-safe, so it'll be the user's responsibility to ensure the value is there.