add note where to get ICONs

Code-Standards.md

@@ -151,6 +151,10 @@ Every layout must have components with defined ID's. Example,
     android:textColorLink="@color/lightBlue" />
 ```
 
+### ICONs are taken from Feathericons
+If an symbole is needed and not included in GitNex jet. Search for on in the [Feather Icon Colection](https://feathericons.com/).
+copy the svg data into an xml file at `app/src/main/res/drawable/`.
+
 #### String names
 All the string names in `strings.xml` must be meaningful. Also check for the string if it is already defined.