fix: Correct critical bugs and improve code quality

[gambinoxxx]

This commit addresses several critical bugs and improves the overall code quality in various game implementations within the repository.

• C++ Hangman Game (Hangman.cpp):

  • Resolved a critical buffer overflow that caused crashes by correctly sizing std::string variables before use.
  • Replaced unsafe C-style string loops with modern C++ std::string::length() checks for better safety and clarity.
  • Substituted the non-portable system("clear") with a cross-platform alternative for screen clearing.

• JavaScript Dodgeball Game (loginregister.html):

  • Fixed a bug where login and registration forms used duplicate HTML id's, causing incorrect element selection in JavaScript.
  • Added a security warning regarding the insecure practice of storing passwords in localStorage.

• JavaScript ConnectFour Game (registration.js):

  • Completed the showRankingsTable function, which was missing the logic to generate and display the rankings table from localStorage data.

These changes ensure the applications run more reliably and adhere to better coding and security practices.