Move all side effects to exported init function

[jeanfredrik]

I’m creating a package that uses yett under the hood and the way it requires an assigned whitelist/blacklist before the package is included makes it hard to use it with import/export because the load order can’t always be guaranteed. This pull request moves all immediate side-effects to an init function that’s exported along with the current unblock function. It still allows setting a whitelist/blacklist on window but also accepts it as an argument to the init function.

Usage before:

    <script>
        window.YETT_BLACKLIST = [
            /script\.js$/
        ]
    </script>
    <script src="yett.min.js"></script>

Usage after:

    <script src="yett.min.js"></script>
    <script>
        yett.init({
            blacklist: [
                /script\.js$/
            ]
        })
    </script>

It would be a breaking change though because nothing will happen unless init is called. If that’s a problem there could perhaps be separate builds for browser and modules.

Tests pass.

[aoumiri]

Exactly what I had in mind when trying this superb library, hope it gets released soon 👍