`importHelpers` generates code, that is incompatible with browsers

Currently enabling importHelpers adds

import * as tslib_1 from "tslib";

at the top of every source file.

Such notation is not compatible with browsers. Nowadays, all modern browsers supports Ecma modules, there's no reason for writing code that assumes Node.js environment + bundler build. Code should assume "Ecma modules" environment instead. And bundlers can stop being compilers and do the work they are supposed to do - create optimized builds (if needed at all).

The change is simple, importHelpers should generate:

import * as tslib_1 from "../../../node_modules/tslib/index.js";

The path to "node_modules" should be determined at compile time of course.

Inizia tracciando il codice del compilatore TypeScript che emette l’import di tslib di importHelpers. Confronta lo specificatore di modulo attuale con il percorso compatibile con il browser richiesto, quindi verifica che l’import generato venga risolto da un ambiente Ecma modules e che il percorso node_modules venga determinato in fase di compilazione.