Use microbundle instead of Webpack

[bakerkretzmar]

This PR replaces Webpack with microbundle, which uses Rollup under the hood. Microbundle is faster, the output is smaller, and there's way less to install and configure.

I also tweaked the outputs/targets:

• route.js is the default (main, umd:main, unpkg, and browser), it's a UMD build that should work basically everywhere
• route.m.js is an ES module (module)
• route.es.js is an ES module specifically targeting modern browsers, so it's a bit smaller and faster than route.m.js
• there's no CommonJS/Node build—route.js should just work, bundlers or packages like esm can be used to import route.m.js if necessary, and Ziggy's target environment is the browser anyway

All tests pass on all of these builds, but I'll keep playing around with this in real apps and in the browser before it's merged.

See also Writing a small module in 2018

[ankurk91]

We can disable source maps with --sourcemap option.

[bakerkretzmar]

If someone doesn't want to use the default route.js build, they can specify which build they want to import in one of two ways:

Import a specific file:

import route from 'ziggy-js/dist/route.es.js';

Use a Webpack alias:

// in webpack.mix.js

mix.webpackConfig({
    resolve: {
        alias: {
            ziggy: 'ziggy-js/dist/route.es.js',
        },
    },
});

// in app.js or anywhere else

import ziggy from 'ziggy';