Use eval('require') instead of require to avoid bundler error

[hzy]

Use eval('require') instead of require to avoid bundler error.

This allow this package continue work with Node.js and can avoid a bundler error.

This PR fixes #11

[hzy]

@papnkukn Would u PTAL :) ?

[aralroca]

I think make sense to avoid Webpack errors

[trasherdk]

It makes more sense to avoid eval() at any cost.

[Tofandel]

Can't we provide a build for browsers without the save function and one for node?

NPM provides the feature to automatically import the correct version using

"exports": {
    "browser": {
      "default": "./qrcode.browser.min.js",
    },
    "default": "./qrcode.min.js",
}