Mostly done with Synths detail page Other minor edits to other pages as well.

Add user guide pages for more event modules key event done (look at the railroad diagram!), outside events done, and valueChange done. Some minor edits to the index page and delegation page.

Event user guide redux WIP. Most of the core sections (basics, delegation, and synths) and supporting pages. Still needs a few synths' supporting pages completed, the advanced options, the FAQ, and the Appendix A of whitelisted DOM events.