add: new input scanning exercises

23-input-scanning/exercises/03-unique-words-2/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+// ---------------------------------------------------------
+// EXERCISE: Unique Words 2
+//
+//  Use your solution from the previous "Unique Words"
+//  exercise.
+//
+//  Before adding the words to your map, remove the
+//  punctuation characters and numbers from them.
+//
+//
+// BE CAREFUL
+//
+//  Now the shakespeare.txt contains upper and lower
+//  case letters too.
+//
+//
+// EXPECTED OUTPUT
+//
+//  go run main.go < shakespeare.txt
+//
+//   There are 100 words, 69 of them are unique.
+//
+// ---------------------------------------------------------
+
+func main() {
+	// This is the regular expression pattern you need to use:
+	// [^A-Za-z]+
+	//
+	// Matches to any character but upper case and lower case letters
+}