JSRenderer implements Renderer against the browser's DOM.
NewJSRenderer will create a new JSRenderer with the speicifc mount point selector. If an empty string is passed then the root component should include a top level <html> tag and the entire page will be rendered.
EventEnv returns an EventEnv that can be used for synchronizing updates.
EventWait blocks until an event has occurred which causes a re-render. It returns true if the render loop should continue or false if it should exit.
Release calls release on any resources that this renderer allocated.
Render is a render function.