perf(explorer): client side explorer (#1810)

* start work on client side explorer

* fix tests

* fmt

* generic test flag

* add prenav hook

* add highlight class

* make flex more consistent, remove transition

* open folders that are prefixes of current path

* make mobile look nice

* more style fixes

quartz/util/clone.ts

@@ -0,0 +1,3 @@
+import rfdc from "rfdc"
+
+export const clone = rfdc()