fix(Checkpoints): add the mains for the exams exercises to work in the code editor

subjects/printnbrbase/main.go

@@ -0,0 +1,20 @@
+package main
+
+import (
+	"piscine"
+
+	"github.com/01-edu/z01"
+)
+
+func main() {
+	piscine.PrintNbrBase(125, "0123456789")
+	z01.PrintRune('\n')
+	piscine.PrintNbrBase(-125, "01")
+	z01.PrintRune('\n')
+	piscine.PrintNbrBase(125, "0123456789ABCDEF")
+	z01.PrintRune('\n')
+	piscine.PrintNbrBase(-125, "choumi")
+	z01.PrintRune('\n')
+	piscine.PrintNbrBase(125, "aa")
+	z01.PrintRune('\n')
+}

subjects/splitwhitespaces/main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	fmt.Printf("%#v\n", piscine.SplitWhiteSpaces("Hello how are you?"))
+}

subjects/swap/main.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	a := 0
+	b := 1
+	piscine.Swap(&a, &b)
+	fmt.Println(a)
+	fmt.Println(b)
+}