Add options: input_position,loading

[dwdh]

PR Checklist

• [x] The commit message follows guidelines for NexT.
• [x] 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.
• [x] Feature.
• [ ] Code style update (formatting, local variables).
• [ ] Refactoring (no functional changes, no api changes).
• [ ] Documentation.
• [ ] Translation.
• [ ] Other... Please describe:

What is the current behavior?

Issue resolved:

What is the new behavior?

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

How to use?

In site _config.yml:

# For more information: https://giscus.app/
giscus:
  enable: false
  repo: # Github repository name
  repo_id: # Github repository id
  category: # Github discussion category
  category_id: # Github discussion category id
  # Available values: pathname | url | title | og:title
  mapping: pathname
  # Available values: 0 | 1 
  reactions_enabled: 1
   # Available values: 0 | 1 
  emit_metadata: 1
  # Available values: light | dark | dark_high_contrast | transparent_dark | preferred-color-scheme
  theme: light
  # Available values: en | zh-C
  lang: en
  # Available value: anonymous 
  crossorigin: anonymous
  # Place the comment box above the comments
  input_position: bottom
  # Load the comments lazily
  loading: