esm types break TypeScript compilation with lib check enabled.

[philkunz]

/node_modules/engine.io-parser/build/esm/index.d.ts (3,57): Relative import paths need explicit file extensions in EcmaScript imports when '--moduleResolution' is 'node12' or 'nodenext'. Did you mean './commons.js'?

Extensions ARE REQUIRED in esm type modules.

[darrachequesne]

This should be fixed by a421bbe, included in engine.io-parser@5.0.4.