docs(contributrors): add ambaradan as a contributor for code

…ocdias

docs(contributrors): add augustocdias as a contributor for code

docs(contributrors): add SuniRein as a contributor for code

docs(contributors): add webdavis as a contributor for ideas

Add automatic completion timestamps when checking tasks, similar to
Obsidian-style task tracking. When enabled, checking a checkbox appends
a configurable timestamp to the task line.

Features:
- Four timestamp formats: emoji, comment, dataview, parenthetical
- Configurable date format via os.date() format string
- Option to remove timestamp on uncheck
- Option to update existing timestamp when re-checking

Configuration:
  list = {
    checkbox_completion = {
      enabled = false,
      format = "emoji",
      date_format = "%Y-%m-%d",
      remove_on_uncheck = true,
      update_existing = true,
    },
  }

Closes #186

…mestamps

feat(list): add checkbox completion timestamps

- Add smart_paste module require
- Call smart_paste.setup() in M.setup()
- Add <Plug>(MarkdownPlusSmartPaste) keymap with default <leader>mp

Add comprehensive tests for smart_paste helper functions:
- _is_url: URL detection (http/https, paths, queries, fragments)
- _html_unescape: HTML entity decoding
- _parse_title: HTML title extraction (og:title, twitter:title, <title>)

- Add smart paste feature description to vimdoc
- Add configuration options to config section
- Add <Plug>(MarkdownPlusSmartPaste) to plug mappings
- Add smart_paste API documentation
- Add curl health check for smart paste feature
- Minor stylua formatting in validate.lua

Some sites (like lua.org) use uppercase <TITLE> tags. The title
extraction pattern now handles any case combination.

Add tests for uppercase and mixed-case title tags.

- Add buffer modifiability check before initial placeholder insertion
- Add buffer modifiability check in cancel path of prompt_for_title
- Handle URLs with special characters (parentheses, spaces) by wrapping
  in angle brackets per markdown spec
- Add url_needs_brackets and format_url_for_markdown helper functions
- Add 13 new tests for URL formatting helpers