Update version to 6.3.0; add configurable truthy condition values, improve condition handling, and refactor config messages

- **Configurations**:
- Introduced `truthyConditionValues` for customizable condition evaluation (`true`, `yes`, etc.) within conditions.
- Updated `config.yml` and `custom_gui.yml_example` to reflect new `truthy-values` option with expanded documentation.
- Added `%prefix%` support across configurable messages for easier customization.
- Refactored config messages to include a global prefix for improved consistency and user experience.

- **Parsing/Validation**:
- Enhanced slot validation in `Config`, issuing warnings for missing or invalid slots in custom items.
- Improved condition logic in `GUIUtils` to match against `truthyConditionValues` for greater flexibility.
- Added better error handling with warnings for unrecognized operators in conditional expressions.

- **Listeners**:
- Updated `InventoryListener` to handle additional edge cases in inventory interactions (e.g., shift-click within custom GUIs).

- **Other Changes**:
- Minor refactoring, improved readability with updated method calls and local variable usage.
- Updated dependencies and plugin compatibility for plugin behavior consistency.