Rename harriscorner.py to harris_corner.py (TheAlgorithms#4470)

* Rename harriscorner.py to harris_corner.py

* updating DIRECTORY.md

* Rename meanthreshold.py to mean_threshold.py

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

Author: cclauss

DIRECTORY.md

@@ -97,8 +97,8 @@
   * [Peak Signal To Noise Ratio](https://github.com/TheAlgorithms/Python/blob/master/compression/peak_signal_to_noise_ratio.py)
 
 ## Computer Vision
-  * [Harriscorner](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/harriscorner.py)
-  * [Meanthreshold](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/meanthreshold.py)
+  * [Harris Corner](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/harris_corner.py)
+  * [Mean Threshold](https://github.com/TheAlgorithms/Python/blob/master/computer_vision/mean_threshold.py)
 
 ## Conversions
   * [Binary To Decimal](https://github.com/TheAlgorithms/Python/blob/master/conversions/binary_to_decimal.py)
@@ -874,6 +874,7 @@
   * [Random Pivot Quick Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/random_pivot_quick_sort.py)
   * [Recursive Bubble Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/recursive_bubble_sort.py)
   * [Recursive Insertion Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/recursive_insertion_sort.py)
+  * [Recursive Mergesort Array](https://github.com/TheAlgorithms/Python/blob/master/sorts/recursive_mergesort_array.py)
   * [Recursive Quick Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/recursive_quick_sort.py)
   * [Selection Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/selection_sort.py)
   * [Shell Sort](https://github.com/TheAlgorithms/Python/blob/master/sorts/shell_sort.py)