feat: fix arrow spread pitch issue and prevent mixed left/right clicks

• Fixed side arrow pitch calculation so left/right arrows stay level with the center arrow, even when looking up or down
• Changed side arrow spread to ±20° using yaw-based direction math for consistent spacing
• Added click-side lock system to prevent firing with left click while holding right click and vice versa
• Introduced HOLD_WINDOW_MS (250ms) to define how long the opposite click is blocked
• Cleaned up PlayerInteractEvent logic for easier maintenance
• Preserved original arrow damage, velocity, and sound behavior
• Bump Spigot API to 1.21.8.
• Change base package from me.vermeil to dev.mitra88.

Full Changelog: https://github.com/Mitra-88/Terminator/compare/v1.7.0...1.8.0