chore: add .markdownlint configuration

[TheMagamed78]

Added a .markdownlint.json file to maintain consistent style and high-quality formatting for all Markdown documentation files.

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Note

Low Risk
Low risk because it only introduces a lint configuration file and does not change runtime code or behavior.

Overview
Adds a new .markdownlint.json to enable default Markdown linting while disabling MD013 (line length), MD033 (inline HTML), and MD041 (first-line heading), and configuring MD024 to only flag duplicate headings among siblings.

^{Written by Cursor Bugbot for commit 15c871d. This will update automatically on new commits. Configure here.}