Add npm lockfile and packageManager info

[IlyaSemenov]

The repo doesn't include lockfile, which is a bad practice. See:

• https://docs.npmjs.com/cli/v10/configuring-npm/package-lock-json: "package-lock.json ... is intended to be committed into source repositories"
• https://pnpm.io/git: "You should always commit the lockfile (pnpm-lock.yaml)."

Please commit the lockfile of whatever package manager you use. Also, please consider setting "packageManager" under package.json, see https://nodejs.org/api/packages.html#packagemanager.