e2e tests

We try to standardize how we build, bundle and publish each plugin. To verify that we are doing this correctly for the ecosystem as a whole we have a set of e2e tests.

Things we currently verify :

• can we use plugins with postcss-loader?
• can we bundle plugins with webpack and use them in a browser?
• can we use TypeScript and import/run plugins?
• can we use plugins with postcss-cli?

We want to be sure that any give change is safe for as many users as possible.

Contributions are welcome.