fix: missing file extension with ESM configuration (#443)

Author: ehmicky

.eslintrc_esm.cjs

@@ -1,4 +1,6 @@
-const baseEslintrc = require('./.eslintrc')
+// CommonJS allows omitting `.js` but not `.cjs`
+// eslint-disable-next-line import/extensions
+const baseEslintrc = require('./.eslintrc.cjs')
 
 // ESLint configuration for packages using pure ES modules.
 // This should be merged to the main `.eslintrc.js` once all our repositories