New highlight themes

[Maxattax97]

PR Checklist

• The commit message follows our guidelines.
• Tests for the changes was maked (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs in NexT website have been added / updated (for features).

PR Type

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

Issue resolved: N/A

What is the new behavior?

• Screenshots with this changes:

• Link to demo site with this changes: N/A

How to use?

In NexT _config.yml:

codeblock:
  # Code Highlight theme
  # Available values: normal | night | night eighties | night blue | night bright | solarized | solarized dark | galactic
  # See: https://github.com/chriskempson/tomorrow-theme
  highlight_theme: solarized dark
  # Add copy button on codeblock
  copy_button:
    enable: true
    # Show text copy result.
    show_result: true
    # Available values: default | flat | mac
    style: flat

Does this PR introduce a breaking change?

• Yes.
• No.

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[1v9]

@all-contributors please add @Maxattax97 for code

[allcontributors]

@1v9

I've put up a pull request to add @Maxattax97! 🎉