fix missing extensions (#101)

Author: spring1843

README.md

@@ -82,7 +82,7 @@ Welcome to **Data Structures and Algorithms in Go**! 🎉 This project is design
         * [Palindrome](./recursion/is_palindrome_test.go)
         * [Climbing Stairs](./recursion/climbing_stairs_test.go)
         * [Exponentiation](./recursion/exponentiation_test.go)
-        * [Regular Expressions Matching](./recursion/)
+        * [Regular Expressions Matching](./recursion/regular_expressions_test.go)
     * [Divide and Conquer](./dnc//README.md)
         * [Binary Search](./dnc/binary_search_test.go)
         * [Square Root with Binary Search](./dnc/square_root_test.go)
@@ -107,7 +107,7 @@ Welcome to **Data Structures and Algorithms in Go**! 🎉 This project is design
         * [Is Graph a DAG](./graph/is_dag_test.go)
         * [Topological Sort](./graph/topological_sort_test.go)
         * [Employee Head Count](./graph/employee_headcount_test.go)
-        * [Remove Invalid Parentheses](./graph/remove_invalid_parentheses.go)
+        * [Remove Invalid Parentheses](./graph/remove_invalid_parentheses_test.go)
         * [Cheapest Flights](./graph/cheapest_flights_test.go)
         * [Word Ladder](./graph/word_ladder_test.go)
         * [Network Delay Time](./graph/network_delay_time_test.go)