Use `module.createRequire()` to fix using `require()` in ESM build

[Julian Meinking]

The ESM build is not able to run readFile() correcly, because require('fs') is used. require() is not avaiable in ESM.

critters/packages/critters/src/index.js

Line 149 in 5e32531

 require('fs').readFile(filename, 'utf8', callback); 

The only thing missing, is to add

import { createRequire } from 'module';
const require = createRequire(import.meta.url);

to index.js.