Add screenshots

Author: retlehs

README.md

@@ -2,6 +2,9 @@
 
 A WordPress plugin that returns post content in Markdown format when requested with an `Accept` header set to `text/markdown` or a `?format=markdown` query parameter.
 
+| Query parameter | Accept header |
+|-------------|---------------|
+| ![Screenshot of the plugin output on WP's default Hello World post](https://cdn.roots.io/app/uploads/post-content-to-markdown-hello-world.png?2) | ![Screenshot of the plugin output on WP's default Hello World post (Accept header)](https://cdn.roots.io/app/uploads/post-content-to-markdown-hello-world-curl.png) |
 ## Requirements
 
 PHP 8.1+