Improve the npm package metadata

[stof]

• add metadata that allows npmjs.com to link back to the repository
• add an optional peer dependency on intl-messageformat so that tools being strict about dependency access (pnpm, Yarn PnP mode) can be supported (relates to intl-messageformat dependency missing #336)

To make the package even better, it might make sense to create a README.md, as npmjs.com will render it.

Regarding the intl-messageformat, I'm actually wondering whether it should be defined as a required dependency instead (and then probably a normal dependency, not a peer one) as the way the UMD wrapper is defined does not make it optional when using CommonJS or RequireJS (the require() is always done):

BazingaJsTranslationBundle/Resources/js/translator.js

Lines 5 to 18 in 6fbd01d

	(function (root, factory) {
	if (typeof module === 'object' && module.exports) {
	// Node. Does not work with strict CommonJS, but
	// only CommonJS-like environments that support module.exports,
	// like Node.
	module.exports = factory(require('intl-messageformat'));
	}
	else if (typeof define === 'function' && define.amd) {
	define(['intl-messageformat'], factory);
	}
	else {
	root.Translator = factory(root.IntlMessageFormat);
	}
	}(typeof self !== 'undefined' ? self : this, function (IntlMessageFormat) {

[stof]

I used the existing dev dependency on intl-messageformat 10.x for the peer dependency constraint. The latest version of the package is version 11, which is now shipping in ESM format.