chore: add .md style in editorconfig

[returnToInnocence]

Purpose of the PR

In view of the confusion caused by the truncation problem after markdown file formatting when you use the code format function of idea, this pr makes a correction. For markdown files, automatic line breaking is no longer carried out, and other formats are still in accordance with the default configuration of idea

Main Changes

• add configuration max_line_length = off

Verifying these changes

• Trivial rework / code cleanup without any test coverage. (No Need)
• Already covered by existing tests, such as (please modify tests here).
• Need tests and can be verified as follows:
  • After pulling the latest editorconfig file, close idea, open it again (this is very important), and enable code format to see if the markdown file is formatted as expected

Does this PR potentially affect the following parts?

• Dependencies (add/update license info & regenerate_dependencies)
• Modify configurations
• The public API
• Other affects (typed here)
• Nope

Documentation Status

• Doc - TODO
• Doc - Done
• Doc - No Need
  • This is because the file format configuration is enabled by default

[imbajin]

no idea why remove the space but could ignore it~