php-wasm/node: Ship as ESM and CJS

[adamziel]

The @php-wasm/node package used to be CommonJS only. This created tricky dependency identity problems in ESM applications, e.g. in #1577 the main script imports the ESM version of @php-wasm/universal, but @php-wasm/node imports the CJS version of it.

This PR ensures @php-wasm/node has an ESM version available.

This is first step towards solving #1583

Closes #1579 Closes #1577

Testing instructions

Run npm run build, copy the built packages from dist/packages/php-wasm to node_modules in another directory, create a test.js script with the following contents:

import { PHP } from '@php-wasm/universal';
import { loadNodeRuntime, useHostFilesystem } from '@php-wasm/node';

const php = new PHP(await loadNodeRuntime('8.0'));
console.log("Hey");
console.log(await php.run({ code: 'echo "Hello, World!";' }));

Then create a package.json file with {"type":"module"} and confirm that running test.js works. Then create test.cjs file as follows:

const { PHP } = require('@php-wasm/universal');
const { loadNodeRuntime } = require('@php-wasm/node');

async function main() {
    const runtimeId = await loadNodeRuntime('8.0');
    console.log({runtimeId})
    const php = new PHP(runtimeId);

    console.log(php);
}
main();

And confirm this one works, too.