Question 157: fix punctuations

README.md

@@ -3077,12 +3077,12 @@
         1. [abc]: Used to find any of the characters between the brackets(a,b,c)
         2. [0-9]: Used to find any of the digits between the brackets
         3. (a|b): Used to find any of the alternatives separated with |
-     2. **Metacharacters:** These are characters with a special meaning
+     2. **Metacharacters:** These are characters with a special meaning.
         For example, below are some use cases,
         1. \\d: Used to find a digit
         2. \\s: Used to find a whitespace character
         3. \\b: Used to find a match at the beginning or ending of a word
-     3. **Quantifiers:** These are useful to define quantities
+     3. **Quantifiers:** These are useful to define quantities.
         For example, below are some use cases,
         1. n+: Used to find matches for any string that contains at least one n
         2. n\*: Used to find matches for any string that contains zero or more occurrences of n