Refactor Algolia search: drop instantsearch.js

[stevenjoezhang]

PR Checklist

• The commit message follows guidelines for NexT.
• 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 (formatting, linting).
• Refactoring (no functional changes).
• Documentation.
• Translation.
• Other... Please describe:

What is the current behavior?

Issue resolved: #794

TBD:

• Debounce
• Use <mark class="search-keyword"></mark>

What is the new behavior?

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

How to use?

In NexT _config.yml:

[github-actions]

This pull request contains changes to the configuration file. Please make sure the documentation in NexT website is changed or added.
Please edit relevant source files here: https://github.com/next-theme/theme-next-docs/tree/master/source/docs and create a pull request with the changes here: https://github.com/next-theme/theme-next-docs/pulls

[coveralls]

Pull Request Test Coverage Report for Build 8982344224

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 97.421%

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Totals
Change from base Build 8909607057:	0.0%
Covered Lines:	395
Relevant Lines:	400

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💛 - Coveralls