Best guess at injecting GitHub usernames into src/_data/sites/*.json files.

11ty-website-sites-to-github.mjs

import cp from "node:child_process";

import fse from "fs-extra";
import fetch from "node-fetch";
import glob from "fast-glob";

const files = await glob("*.json");

for (const file of files) {
  // Pipe through `tail -1` to get original commit, set encoding to "utf-8" instead of default "buffer".
  const firstCommit = cp.execSync(`git log --follow --format=oneline ${file} | tail -1`, {encoding: "utf-8"});
  // Pluck the first row item which is the Git SHA of the commit.
  const sha = firstCommit.split(/\s/, 1)[0];

  // Fetch commit from repo using GitHub API so we can get the GitHub username of original PR author.
  const res = await fetch(`https://api.github.com/repos/11ty/11ty-website/commits/${sha}`);
  const body = await res.json();
  const githubUsername = body.author.login;
  const site = await fse.readJson(file);
  site.github = githubUsername;
  console.log({file, site});
  // await fse.writeJson(file, site);
}

README.md

NOTE: I added this 11ty-website-sites-to-github.mjs file in the ./src/_data/sites/ directory, so it's looking for the *.json files in the current directory.