feat: Implement "Open in Opposite Group" command

[sfyr111]

Summary

This PR introduces the "Open in Opposite Group" feature, which allows users to open the active editor tab in the opposite editor group with a single command. This functionality enhances navigation efficiency and aligns with similar features found in IntelliJ IDEA.

Changes

• Added a new command intellij.openInOppositeGroup in IntellijExtension class.
• Registered the new command in the extension's activate function.
• Updated package.json to include the new command and its keybindings.
• Ensured the command maintains focus on the newly opened editor tab and toggles back when invoked again.

Impact

This feature is expected to significantly improve user experience for those working with multiple files across different editor groups, making it easier to compare and edit files side by side.

Testing

• Manual testing was conducted to ensure the command behaves as expected in various scenarios, including single and multiple editor groups.
• Focus behavior and toggle functionality were verified to ensure consistency with the intended user experience.

Resolves #336

[sfyr111]

@kasecato ,

Thank you for your review and the valuable feedback. I've made the suggested changes. Please let me know if there's anything else that needs attention or further modification.

I appreciate your guidance!

[kasecato]

I'd personally like to bind and use it. Thanks for your contribution