* fix: update to latest sapper
fixes#416
* fix error and debug pages
* requestIdleCallback makes column switching feel way nicer than double rAF
* add export feature
* add better csp info
* workaround for sapper sub-page issue
* clarify in readme about exporting
* fix now config
* switch from rIC to triple raf
* style-loader is no longer used
* update theming guide
The point of this PR is to make it easier to implement scrollbars (#683).
With this PR, the themes move from a body tag-based system (e.g. `body.theme-scarlet`) to a system where they simply declare global CSS and we use CSS specificity order to give us the right theme.