Adding string lowering example

stringLower.cpp

@@ -0,0 +1,20 @@
+#include <iostream>
+#include <string>
+#include <cctype>
+using namespace std;
+
+string wholeLower(string s){
+  for(int i = 0; i < s.length(); i++){
+    s[i] = tolower(s[i]);
+  }
+  return s;
+}
+
+int main(){
+  string ourStr;
+  cout << "Enter a string. Just try to yell if you can!" << endl;
+  cin >> ourStr;
+
+  ourStr = wholeLower(ourStr);
+  cout << "Here's the string you entered (but whispering) " << ourStr << endl;
+}