Add next/previous functionality:
- clickable arrows and keyboard control
- new endpoint to posts API to get next/previous IDs
- refactor UI position functions as a subset ‘position’
Update genericons with correct asset location
Remove commented out code
Trigger a new page view on single-post-close if we don’t have anything inside #main-content (there are not already posts loaded)
Add an animation for each item on load
Clean up view js & shrink the distance animated