Update README.md

Add url to example, how use electron-updater from gitlab.com private repository

Author: Slauta

README.md

@@ -3,6 +3,7 @@ This repo contains the **bare minimum code** to have an auto-updating Electron a
 If you can't use GitHub, you can use other providers:
 
 - [Complete electron-updater HTTP example](https://gist.github.com/iffy/0ff845e8e3f59dbe7eaf2bf24443f104)
+- [Complete electron-updater from gitlab.com private repo example](https://gist.github.com/Slauta/5b2bcf9fa1f6f6a9443aa6b447bcae05)
 
 **NOTE:** If you want to run through this whole process, you will need to fork this repo on GitHub and replace all instances of `iffy` with your GitHub username before doing the following steps.