Convert project to ESM

[audiodude]

EDIT: This PR now converts the entire project to ESM. I have tested npm install and it seems to be working for me on Linux. A quick scan of the build scripts doesn't reveal any imported calls that are made in only one branch, so I think it's safe.

Original PR message below.

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Trying to import @openzim/libzim into mwoffliner.

It was building fine but I was getting this error when trying to run the JS:

$ node ./lib/cli.js --webp --mwUrl="https://bm.wikipedia.org/" --format="nopic:nopic" --format="novid:maxi" --osTmpDir="/dev/shm" --adminEmail="contact@kiwix.org" --outputDirectory="output" --customZimFavicon="https://drive.farm.openzim.org/wikipedia_all/favicon-48x48.png" --customZimDescription="offline version of Wikipedia in Bambara" --publisher="openZIM" --forceRender=WikimediaMobile
file:///home/tmoney/code/mwoffliner/lib/util/misc.js:11
import { StringItem } from '@openzim/libzim';
         ^^^^^^^^^^
SyntaxError: Named export 'StringItem' not found. The requested module '@openzim/libzim' is a CommonJS module, which may not support all module.exports as named exports.
CommonJS modules can always be imported via the default export, for example using:

import pkg from '@openzim/libzim';
const { StringItem } = pkg;

    at ModuleJob._instantiate (node:internal/modules/esm/module_job:123:21)
    at async ModuleJob.run (node:internal/modules/esm/module_job:191:5)
    at async ModuleLoader.import (node:internal/modules/esm/loader:337:24)
    at async loadESM (node:internal/process/esm_loader:34:7)
    at async handleMainPromise (node:internal/modules/run_main:106:12)

Node.js v18.20.3

When I tried a test.ts with the following:

import * as libzim from '@openzim/libzim'

console.log(libzim)

I got:

 node lib/test.js
(node:1259347) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/home/tmoney/code/node-libzim/dist/index.js:1
import bindings from "bindings";
^^^^^^

SyntaxError: Cannot use import statement outside a module
    at internalCompileFunction (node:internal/vm:76:18)
    at wrapSafe (node:internal/modules/cjs/loader:1283:20)
    at Module._compile (node:internal/modules/cjs/loader:1328:27)
    at Module._extensions..js (node:internal/modules/cjs/loader:1422:10)
    at Module.load (node:internal/modules/cjs/loader:1203:32)
    at Module._load (node:internal/modules/cjs/loader:1019:12)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/translators:203:29)
    at ModuleJob.run (node:internal/modules/esm/module_job:195:25)
    at async ModuleLoader.import (node:internal/modules/esm/loader:337:24)
    at async loadESM (node:internal/process/esm_loader:34:7)

Node.js v18.20.3

Which led me to believe that upstream (this package) had the error.

As far as I understand, the import keyword can only be used in ESM and Typescript, so this does appear to be a bug.