Added KMP to index under String algorithms section.

Author: dragonslayerx

README.md

@@ -72,6 +72,7 @@ Collection of algorithms and data structures in C++ used widely in Competitive p
 * **Strings** :
    * *String Algorithms* :
        * [Z Algorithm](https://github.com/dragonslayerx/Competitive-Programming-Repository/blob/master/src/Z_algorithm_max_prefix_match.cpp)
+       * [KMP algorithm](https://github.com/dragonslayerx/Competitive-Programming-Repository/blob/master/src/KMP.cpp)
        * [Rolling String Hashing](https://github.com/dragonslayerx/Competitive-Programming-Repository/blob/master/src/string_hashing.cpp)
        * [Rolling String Hashing for Dynamic Strings](https://github.com/dragonslayerx/Competitive-Programming-Repository/blob/master/src/string_hashing_dynamic_segment_trees.cpp)
    * *String Data Structures* :