Markdown style guide as basement of project (might be done partly)

[ValentinKarnaukhov]

As this project is based on markdown, so we need to write markdown style guide in order to have single formatting, style, etc.

It should be done by technical writer or person with experience of technical documentation (but anybody are welcome).

New style guide should be located at /language/markdown/code_style/markdown_code_style_en.md