Add sponsor message by @instabug (#595)

contents.json

@@ -4,7 +4,7 @@
   "description": "<!-- \n⚠️ This README is generated, please do not update. To contribute, make changes to contents.json ⚠️ \n https://github.com/dkhamsing/open-source-ios-apps -->",
   "header": "```\n 100+ Stars: 🔥\n 200+ Stars: 🔥🔥\n 500+ Stars: 🔥🔥🔥\n1000+ Stars: 🔥🔥🔥🔥\n2000+ Stars: 🔥🔥🔥🔥🔥\n\nProjects are in English unless indicated by flags \n🇨🇳 Project is in Chinese\n🇪🇸 Project is in Spanish\n... \n\nClick ► to show more details\n```",
   "footer": "## Thanks\n\nThis list was inspired by [awesome-ios](https://github.com/vsouza/awesome-ios) and [awesome-swift](https://github.com/matteocrippa/awesome-swift). Thanks to all the [contributors](https://github.com/dkhamsing/open-source-ios-apps/graphs/contributors) 🎉 \n\n## Contact\n\n- [github.com/dkhamsing](https://github.com/dkhamsing)\n- [twitter.com/dkhamsing](https://twitter.com/dkhamsing)\n- [github.com/vpeschenkov](https://github.com/vpeschenkov)\n",
-  "sponsor": "",
+  "sponsor": "## Supported with :heart: by [Instabug](https://try.instabug.com/ios/?utm_source=opensourceios&utm_medium=spon&utm_content=header) \n[![react-native](https://user-images.githubusercontent.com/9888943/35385975-e6829fc0-01d2-11e8-963f-2166c4a67763.gif)](https://try.instabug.com/ios/?utm_source=opensourceios&utm_medium=spon&utm_content=banner) \n> We highly recommend using Instabug’s SDK while betatesting to receive detailed bug and crash reports from early adopters. \nThe SDK removes the hassle of debugging by automatically attaching screen recordings, device details, network logs, and repro-steps with each report to help you speed up the development process. [**Learn more.**](https://try.instabug.com/ios/?utm_source=opensourceios&utm_medium=spon&utm_content=learnmore) 🚀 \n[![](https://instabug-ga.appspot.com/UA-41982088-6/github/opensourceios?pixel)](https://instabug.com)",
   "categories": [
     {
       "title": "Apple TV",