What is Markdown?
Markdown is a lightweight markup language with plain text formatting syntax. It is designed so that it can be converted to HTML and many other formats using a tool by the same name. Markdown is often used to format readme files, for writing messages in online discussion forums, and to create rich text using a plain text editor. As the initial description of Markdown contained ambiguities and unanswered questions, many implementations and extensions of Markdown appeared over the years to answer these issues.
To install markdown, you need to install Markdown filter module and Markdown editor module. 1. Markdown filter: https://www.drupal.org/project/markdown 2. Markdown editor: https://www.drupal.org/project/simplemde
Download both modules into modules folder in your drupal site. When you try to install modules, you will see error message that require markdown library. Markdown filter is require "drupal/markdown" library. To install it, run composer command:
composer require drupal/markdown
After download drupal/markdown library, you can install markdown and simplatemde modules nomarly.
Config Markdown text format
To use markdown, you create new text format (example Markdown). Go to Configuration => Content authoring => Text formats and editors and click "Add text format" button. Under Enabled filters list, check on Markdown checkbox
Scrolldown and click on Markdown tab, set Markdown library value to PHP Markdown and save.
That all, and now you have Markdown editor on your Drupal site.