Update citation to journal paper

Author: ahmedfgad

README.md

@@ -311,13 +311,13 @@ Find the book at these links:
 If you used PyGAD, please consider adding a citation to the following paper about PyGAD:
 
 ```
-@misc{gad2021pygad,
-      title={PyGAD: An Intuitive Genetic Algorithm Python Library}, 
-      author={Ahmed Fawzy Gad},
-      year={2021},
-      eprint={2106.06158},
-      archivePrefix={arXiv},
-      primaryClass={cs.NE}
+@article{gad2023pygad,
+  title={Pygad: An intuitive genetic algorithm python library},
+  author={Gad, Ahmed Fawzy},
+  journal={Multimedia Tools and Applications},
+  pages={1--14},
+  year={2023},
+  publisher={Springer}
 }
 ```
 

docs/source/index.rst

@@ -228,13 +228,13 @@ details:
 
 .. code:: 
 
-   @misc{gad2021pygad,
-         title={PyGAD: An Intuitive Genetic Algorithm Python Library}, 
-         author={Ahmed Fawzy Gad},
-         year={2021},
-         eprint={2106.06158},
-         archivePrefix={arXiv},
-         primaryClass={cs.NE}
+   @article{gad2023pygad,
+     title={Pygad: An intuitive genetic algorithm python library},
+     author={Gad, Ahmed Fawzy},
+     journal={Multimedia Tools and Applications},
+     pages={1--14},
+     year={2023},
+     publisher={Springer}
    }