Updated README.md

    - Added a column for Elixir in each table.
    - Mapped the scripts. 
    - Replaced references to multiple online compilers with one singular compiler. 
    - Added instructions on how to access compiler sites for each language. 
    - Centered the title. 
    - Added the Back to top button. 
    - Finally, linked each topic/item to its specific site.

Author: TestingGround00