* 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
Part of the way to improving #390.
Before this fix, if you recieved a notification while Pinafore was in a background tab, nothing would happen, because most browsers (Edge, Firefox, Chrome) don't run rAF in background tabs. Furthermore, Chrome doesn't run rIC. In this PR we detect if we're in a background tab and then avoid rAF/rIC in that case.