add jekyll-postfiles usage to cheatsheet

Author: 0xdevalias

README.md

@@ -10,6 +10,11 @@ Feel free to create an issue/pull request for any typo's/bugs you might find :)
 
 * Link to other posts
     * `[other post]({% post_url 2017-01-01-other-post %})`
+* Embed an image with [jekyll-postfiles](https://github.com/nhoizey/jekyll-postfiles#how-does-it-work)
+  * create a folder under `_posts` named the same as your post's markdown file
+  * add any images for your post there, along with the post's markdown file
+  * use a relative markdown image tag to reference and embed the images
+    * eg. `![a title or something](foo.jpg)`
 * Embed a gist with [jekyll-gist](https://github.com/jekyll/jekyll-gist)
     * `{% gist foo/12345678901234567890 %} `
 * Embed a tweet with [jekyll-twitter-plugin](https://github.com/rob-murray/jekyll-twitter-plugin)