badge-maker: fix exports so that it can also be required

[vidarc]

Requiring ESM was ported back to version 20.19.0 of NodeJS, so this PR fixes the exports field so that you can do so. Only requirement is that there is no top-level await for it to work, which doesn't look like this package relies on anyway.

before

Welcome to Node.js v20.19.2.
Type ".help" for more information.
> require('badge-maker')
Uncaught:
Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /.../node_modules/badge-maker/package.json
    at exportsNotFound (node:internal/modules/esm/resolve:322:10)
    at packageExportsResolve (node:internal/modules/esm/resolve:613:13)
    at resolveExports (node:internal/modules/cjs/loader:636:36)
    at Module._findPath (node:internal/modules/cjs/loader:716:31)
    at Module._resolveFilename (node:internal/modules/cjs/loader:1198:27)
    at Module._load (node:internal/modules/cjs/loader:1043:27)
    at Module.require (node:internal/modules/cjs/loader:1298:19)
    at require (node:internal/modules/helpers:182:18) {
  code: 'ERR_PACKAGE_PATH_NOT_EXPORTED'
}

after

Welcome to Node.js v20.19.2.
Type ".help" for more information.
> require('badge-maker')
[Module: null prototype] {
  ValidationError: [class ValidationError extends Error],
  makeBadge: [Function: makeBadge]
}

[github-actions]

	Messages
📖	✨ Thanks for your contribution to Shields, @vidarc!

Generated by 🚫 dangerJS against 93344db

[jNullj]

Thank you for the fix.
for anyone looking for docs about this - link, link, link.

[jNullj]

@vidarc fix is now live on npm with ver 5.0.2, enjoy.