Updated Plugin development (markdown)

Plugin-development.md

@@ -23,4 +23,22 @@ Here's the list with links to any plugins that have any relevant information:
 - `scroll` - Allows to navigate with scroll.
 - `touch` - Allows to navigate with touch gestures.
 - `video` - Allows to pause video and autoplay them upon entering the slide.
-- `youtube` - Allows to control YouTube videos.
+- `youtube` - Allows to control YouTube videos.
+
+## Getting started
+
+When creating a new plugin you can use Classes. Something like this:
+
+```javascript
+class MyPlugin {
+  constructor(wsInstance) {
+    // Do your magic 🌟
+  }
+}
+```
+
+The constructor gets the WebSlides instance which allows you to call any of the [public methods](Core-API). 
+
+### Plugins that affect only some slides
+
+There are times in which you may need to add a feature to only certain slides like we do with videos for example.