add auto completion

[heilgar]

Added

• Intelligent Autocompletion System
  • Environment variable completion with {{ trigger
  • HTTP method completion at the start of requests
  • HTTP header name completion with documentation
  • Content type suggestions for Content-Type and Accept headers
  • Adaptive filtering for better matching as you type
  • Robust support for nvim-cmp
  • Fallback completion for vanilla Neovim
  • Caching system for recently used variables
  • Context-aware completion based on cursor position