v1.6.4.6 update: UX and assessment updates

Syntence v1.6.4.6 update:

-new tutorial focusing on independent/dependent sentence parts added

-added "10 questions total" before intro assessment

-fixed some timing issues with cutscenes

-make clear: "Right-click" to go backward or cancel

-confirm why assessment submission works but level data submission is rejected

-add levels completed display (out of 21) [temporary fix]