Module Manager: Write configuration diffs to disk

[dswbx]

This PR adds a plugin that writes down diff entries to disk. Addresses #201

// bknd.config.ts
import type { BkndConfig } from "bknd";
import { writeFile } from "node:fs/promises";

export default {
  options: {
     plugins: [
        syncDiffs({
           enabled: true,
           write: async (name, diffs) => {
              await writeFile(`.diffs/${name}`, JSON.stringify(diffs, null, 2));
           },
        }),
     ],
  }
} as const satisfies BkndConfig;

Todo:

• write down diffs on configuration changes
• potentially adding a timestamp to the config to compare against
• stress test
• add a migration command to apply diffs