Simlified js-components setup

[VojtechVidra]

We can simplify @flows/js-components setup by providing another custom element for example <flows–floating-blocks> that would do the rendering setup of floating blocks for you. As a result the setup of @flows/js-components would be two lines:

• A setup function that takes components as an argument and registers the custom elements
• Adding <flows–floating-blocks> at the end of your body element