Personal reminders doc

[maddaicita]

Summary

This pull request includes enhancements and documentation updates for the UserReminders cog as part of the ongoing effort to improve the ClassMateBot-1.1.
Key Points

Added user-specific reminder system functionality.
Created markdown documentation for each command within the UserReminders cog.
Implemented consistent datetime format validation across commands.
Commands and cogs have updated descriptions for clarity.
Code has been formatted to adhere to PyLint and Black standards.

New Files

docs/UserReminders/add_personal_reminder.md
docs/UserReminders/delete_personal_reminder.md
docs/UserReminders/list_personal_reminders.md
docs/UserReminders/update_personal_reminder.md
docs/UserReminders/check_reminders.md

Changed Files

cogs/userreminders.py - Main cog file with new commands and functionality.
bot.py - Updates to handle new cog loading and command registration.
Updated .md files within the docs/ directory for accurate command usage.
All related cogs for updated command names and descriptions.

Closing Issues

This pull request addresses the following issues:

Improved user-specific reminder functionality [#3](https://github.com/maddaicita/ClassMateBot-1.1/issues/3)
Standardized datetime format for reminders.

All changes have been tested locally and all unit tests are passing, ensuring stable integration into the main project.