Add support for .mjs

[amatiasq]

This enables proper dependency parsing for .mjs files.

[amatiasq]

If someone has this issue with madge, I've come up with this snippet to get a hacked version with this change.

Nasty but works.

// This hack is required because filing-cabinet
// (a madge dependency) doesn't support .mjs files
// https://github.com/dependents/node-filing-cabinet/pull/128

import { readFile, writeFile } from 'fs/promises';

async function getHackedMadge() {
    const file = await import.meta.resolve('filing-cabinet/index.js');
    const content = await readFile(file, 'utf8');

    if (!content.includes('.mjs')) {
        const hacked = content.replace(
            "'.jsx': jsLookup,",
            (x) => `${x}\n  '.mjs': jsLookup,`
        );

        await writeFile(file, hacked, 'utf8');
    }

    const module = await import('madge');
    const madge = module.default ?? module.madge;

    // @ts-ignore This is memoization
    getHackedMadge = () => madge;

    return madge;
}

// anywhere else
const madge = await getHackedMadge();
// following invocations are memoized
const madge2 = await getHackedMadge();
console.assert(madge === madge2)

[XhmikosR]

By the same logic, shouldn't .cjs be supported too?

Note that this needs a test case.