added argv to add any txt file

main.py

@@ -2,12 +2,18 @@ from stats import count_words
 from stats import count_characters
 from stats import sort_by_count
 
+import sys
+
 def get_book_text(filepath):
     with open(filepath) as f:
         return f.read()
 
 def main():
-    read_file = get_book_text("books/frankenstein.txt")
+    if len(sys.argv) < 2:
+        print("Usage: python3 main.py <path_to_book>")
+        sys.exit(1)
+    
+    read_file = get_book_text(sys.argv[1])
     counted = count_words(read_file)
     counted_chars = count_characters(read_file)