docs: add OpenSearch Dashboards Keyboard Shortcuts report for v3.3.0

[tkykenmt]

Summary

This PR adds documentation for the OpenSearch Dashboards Keyboard Shortcuts feature introduced in v3.3.0.

Reports Created

• Release report: docs/releases/v3.3.0/features/opensearch-dashboards/opensearch-dashboards-keyboard-shortcuts.md
• Feature report: docs/features/opensearch-dashboards/keyboard-shortcuts.md

Key Changes in v3.3.0

• Configurable keyboard shortcuts service with opensearchDashboards.keyboardShortcuts.enabled setting
• Help modal accessible via Shift+/ displaying all registered shortcuts
• useKeyboardShortcut React hook for plugin integration
• Pre-registered navigation shortcuts (g d for Discover, g b for Dashboard, g v for Visualization)
• Query editor shortcuts for date picker, refresh, and commenting lines
• Cypress E2E tests for the feature

Related PRs

PR	Description
#10409	Add keyboard shortcuts configuration option
#10455	Add useKeyboardShortcut hook
#10466	Add keyboard shortcut help modal
#10509	Register navigation shortcuts
#10543	Add Cypress tests
#10545	Enable comment shortcuts in Query Editor

Closes #1446