Trigger Search Event when user presses Ctrl + K

[penxian]

PR Checklist

• The changes have been tested (for bug fixes / features).
• Docs in NexT website have been added / updated (for features).

PR Type

• Bugfix.
• Feature.
• Improvement.
• Code style update (e.g. formatting, linting).
• Refactoring (no changes to functionality and APIs).
• Documentation.
• Translation.
• Other... Please describe:

What is the current behavior?

Issue resolved:
Search Services will support shortcut key ctrl + K

What is the new behavior?

• Link to demo site with this changes:
• Screenshots with this changes:
  

How to use?

In NexT _config.yml:

[welcome]

Thanks so much for opening your first PR here!

[CLAassistant]

All committers have signed the CLA.

[coveralls]

Pull Request Test Coverage Report for Build 10956269594

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 97.446%

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Totals
Change from base Build 9517060757:	0.0%
Covered Lines:	400
Relevant Lines:	405

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💛 - Coveralls

[stevenjoezhang]

Thank you for your contribution. I have modified some of the code to support the Cmd+K shortcut on macOS.

[welcome]

Congrats on merging your first pull request here! 🎉 How awesome!