Adding of a new exercise printalt.

The goal: printing the alphabet alternatively with the last and first letter first and so on. zaybxc etc...

go/tests/prog/printalt2_prog/main.go

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+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("zaybxcwdveuftgshriqjpkolnm")
+}

go/tests/prog/printalt2_test/main.go

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+package main
+
+import (
+	"lib"
+)
+
+func main() {
+	lib.ChallengeMain("printalt2")
+}

subjects/printalt2/README.md

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+## printalt2
+
+### Instructions
+
+Write a program that prints the Latin alphabet in lowercase alternatively with the last and first letters, then with the second to last and second letters, and so on until all the alphabet letters are displayed on a single line.
+
+A line is a sequence of characters preceding the [end of line](https://en.wikipedia.org/wiki/Newline) character (`'\n'`).
+
+Please note that `casting` is not allowed for this exercise!
+
+### Usage
+
+```console
+student@ubuntu:~/[[ROOT]]/printalt2$ go build
+student@ubuntu:~/[[ROOT]]/printalt2$ ./printalt2
+zaybxcwdveuftgshriqjpkolnm
+student@ubuntu:~/[[ROOT]]/printalt2$
+```