Update docs/HowSwiftImportsCAPIs.md
Update docs/HowSwiftImportsCAPIs.md

* Increase heading levels
* Update the introduction
* Use `Int` in `qsort` examples
* Use `CInt` in anonymous structs
* Use `CUnsignedInt` in enums
* De-dupe `HomeworkExcuse` enum

jckarter/swift,jmgc/swift,apple/swift,tkremenek/swift,apple/swift,harlanhaskins/swift,aschwaighofer/swift,jckarter/swift,parkera/swift,nathawes/swift,parkera/swift,stephentyrone/swift,parkera/swift,parkera/swift,ahoppen/swift,stephentyrone/swift,atrick/swift,benlangmuir/swift,xwu/swift,jmgc/swift,allevato/swift,glessard/swift,aschwaighofer/swift,CodaFi/swift,harlanhaskins/swift,parkera/swift,hooman/swift,jckarter/swift,roambotics/swift,JGiola/swift,tkremenek/swift,xwu/swift,atrick/swift,stephentyrone/swift,tkremenek/swift,parkera/swift,JGiola/swift,allevato/swift,ahoppen/swift,roambotics/swift,aschwaighofer/swift,atrick/swift,jckarter/swift,rudkx/swift,jmgc/swift,harlanhaskins/swift,gregomni/swift,jmgc/swift,rudkx/swift,hooman/swift,jckarter/swift,jmgc/swift,apple/swift,benlangmuir/swift,allevato/swift,airspeedswift/swift,glessard/swift,tkremenek/swift,nathawes/swift,ahoppen/swift,nathawes/swift,jckarter/swift,nathawes/swift,xwu/swift,hooman/swift,ahoppen/swift,nathawes/swift,airspeedswift/swift,allevato/swift,xwu/swift,airspeedswift/swift,xwu/swift,ahoppen/swift,glessard/swift,aschwaighofer/swift,atrick/swift,jmgc/swift,nathawes/swift,allevato/swift,apple/swift,parkera/swift,xwu/swift,glessard/swift,gregomni/swift,xwu/swift,rudkx/swift,JGiola/swift,ahoppen/swift,allevato/swift,JGiola/swift,harlanhaskins/swift,gregomni/swift,hooman/swift,aschwaighofer/swift,hooman/swift,glessard/swift,atrick/swift,jckarter/swift,parkera/swift,CodaFi/swift,CodaFi/swift,gregomni/swift,rudkx/swift,hooman/swift,JGiola/swift,benlangmuir/swift,glessard/swift,apple/swift,aschwaighofer/swift,rudkx/swift,harlanhaskins/swift,harlanhaskins/swift,airspeedswift/swift,apple/swift,JGiola/swift,hooman/swift,gregomni/swift,roambotics/swift,stephentyrone/swift,tkremenek/swift,benlangmuir/swift,harlanhaskins/swift,aschwaighofer/swift,jmgc/swift,roambotics/swift,CodaFi/swift,allevato/swift,airspeedswift/swift,CodaFi/swift,stephentyrone/swift,atrick/swift,benlangmuir/swift,nathawes/swift,tkremenek/swift,CodaFi/swift,CodaFi/swift,stephentyrone/swift,stephentyrone/swift,airspeedswift/swift,tkremenek/swift,airspeedswift/swift,roambotics/swift,roambotics/swift,benlangmuir/swift,gregomni/swift,rudkx/swift