add description file for every algorithm in Markdown language

[i-vishi]

• Add description file for every algorithm in the repository.
• The file must be written in Markdown language.
• Name of file should be: algorithm_name.md.
• Description file should be inside the algorithm's folder as: ALGORITHM_NAME/algorithm_name.md.
• The file should contain the basic information about the algorithm, i.e., where, why and how it is used.
• It should also contain the pseudocode of the algorithm.