Using C++, write a code that
this program always stores text file output into a text file
named "clean.txt".
-The program should read one character at a time from
"someNumbers.txt", and do the following.
-If it is a letter, print that letter to the screen, AND also
store it in the text file. All letters should be converted to
lowercase beforehand.
-If it is a number, print that number to screen, but do NOT
store it in the text file....