Update README.md

Fixed minor typos.

README.md

@@ -48,8 +48,8 @@ Each data instance contains the following features: correct, wrong and category.
 
 ### Data Fields
 
-- 'Correct': a string containing the a Norwegian sentence with correct use of comma
-- 'Wrong': a string containig the same Norwegian sentence with wrong use of comma
+- 'Correct': a string containing a Norwegian sentence with correct use of comma.
+- 'Wrong': a string containig the same Norwegian sentence with wrong use of comma.
 - 'Category': an integer indicating the rule tested by the pair of correct and wrong sentences.
 
 ### Norwegian comma rules