Support dynamic loading of reaction items, get better defaults

Dynamic loading

Plugin now supports dynamic loading for reaction items. Just trigger the event initAirReactions and new reaction items will be seeked from DOM and initialized.

Example:

// After posts loaded from AJAX
const event = new Event('initAirReactions');
window.dispatchEvent(event);

Better defaults

Get the default reaction types from the filtered type list instead of hard coded defaults.

Thanks to @hoandt for pointing out the issues.