monolog-mysql v2.x (PHP8 support, new features)

[amacado]

This pull request prepares updates for the next major release. If you want to add your new feature please feel free to open a pull request against the v2.x branch to take your feature or bugfix into consideration.

Breaking changes & new features

• [x] Dropped PHP7 support (PHP itself supports only PHP8.1+)
• [x] Added monolog v3 support
• [x] Renamed constructor argument $initialize to $skipTableInitialization for more readability
• [x] Changed order of the constructor arguments
• [ ] Replaced the unix timestamp colum with datetime column (https://github.com/waza-ari/monolog-mysql/pull/40)

Maintenance & Bugfixes

• [x] Updated and created tests for new environment (100% coverage)
• [x] Updated docker-compose to support local development and testing
• [x] https://github.com/waza-ari/monolog-mysql/issues/41