fix(types): fixes cjs types

[micheleriva]

This PR fixes types when using TypeScript via CommonJS modules. It introduces a breaking change in TypeScript, as follows:

- import { create, insert, search } from '@lyrasearch/lyra';
- import { stemmer } from '@lyrasearch/lyra/stemmer/it';
- import { requireLyraInternals } from '@lyrasearch/lyra/internals';

+ import { create, insert, search } from '@lyrasearch/lyra/cjs';
+ import { stemmer } from '@lyrasearch/lyra/cjs/stemmer/it';
+ import { requireLyraInternals } from '@lyrasearch/lyra/cjs/internals';

We basically have to manually tell TypeScript to get types and functions from CommonJS files.

Fixes #243

[ShogunPanda]

LGTM!