Update capitalize.py (TheAlgorithms#10573)

* Update capitalize.py

* Update strings/capitalize.py

---------

Co-authored-by: Tianyi Zheng <tianyizheng02@gmail.com>

Author: 2 people

Diff for: strings/capitalize.py

@@ -3,7 +3,8 @@
 
 def capitalize(sentence: str) -> str:
     """
-    This function will capitalize the first letter of a sentence or a word
+    Capitalizes the first letter of a sentence or word.
+
     >>> capitalize("hello world")
     'Hello world'
     >>> capitalize("123 hello world")
@@ -17,6 +18,10 @@ def capitalize(sentence: str) -> str:
     """
     if not sentence:
         return ""
+
+    # Create a dictionary that maps lowercase letters to uppercase letters
+    # Capitalize the first character if it's a lowercase letter
+    # Concatenate the capitalized character with the rest of the string
     lower_to_upper = dict(zip(ascii_lowercase, ascii_uppercase))
     return lower_to_upper.get(sentence[0], sentence[0]) + sentence[1:]