Many sleek:open events per click in single page application
### Expected Behavior
When I register an event listerner via `window.document.addEventListener('sleek:open', ...)`, exactly one event is dispatched when the widget is opened.
### Current Behavior
When I navigate my single page application causing N pushstate/popstate events, the event is dispatched N+1 times when the widget is opened.
### Possible Solution
The Sleekplan widget script should not re-register click events for elements with data-sleek attribute on each pushstate event.
### Steps to Reproduce
1. Place a data-sleek element on your page
2. Register an event listener for sleek:open
3. Load the Sleekplan JS SDK
4. Trigger multiple pushstate events
5. Get multiple invocations of the event listener
### Context (Environment)
I used the event to report analytics data and started seeing absurd widget open rates per user.
As a workaround I now remove that data-sleek attribute in a sleek:init event handler.