[FEATURE] add upgrade info

Upgrade.md

+# Upgrade from ```6.x.x``` to ```7.x.x```
+
+In Version 7, we rewrote all included JavaScript to ES6 modules. This means that they won't be included in your site automatically when you install the extension.
+
+## Importing the sgnews bundle in your main project
+
+sg_news offers a front-package that imports all sub modules and initilaizes them correctly. You can import this in your bundle like that:
+
+```js
+import SgNews from 'sgnews';
+new SgNews();
+```
+
+### Mapping ```sgnews``` to the extension JavaScript
+
+In order for your module bundler to find the ```sgnews``` package, you need to add the path to your configuration. If you are using the SGC, you can add the following to your ```.sgc-config.json```
+
+```js
+{
+	"js": {
+		"libraryPaths": [
+			...
+			"./web/typo3conf/ext/sg_news/Resources/Public/JavaScript/"
+		]
+	}
+}
+```